To save me some comments and PM's: I've always heard people use "laying out" for sunning. It's apparently an American-only phrase. I know that's grammatically incorrect, but it's what sounds natural to me.

*****

The next day, Monday, was beautiful for water skiing, and we had a great morning session. When Mom or Dad skied, Joanna sat next to me, and Kaitlyn taught her how to be a good lookout.

After lunch, it was nap time for Mom and Dad, which meant the rest of us had to hang out somewhere else for at least an hour. What Kaitlyn and I usually did was lay out on chaise lounges that were halfway between the lake house and the lake. While Mom and Dad cleaned up, Joanna and Kaitlyn went into their bedrooms to change into sunning bikinis. The difference in how busty Joanna and Kaitlyn were was even more obvious when they were in these bikinis. Still, Joanna looked good.

Once we left the lake house, Joanna, Kaitlyn, and I went to the chaise lounges while Paul went over to a hammock in the shade with his tablet. We sprayed sunscreen on each other and then lay down. As I hadn't slept well the last two nights, I was soon fast asleep.

"...to you?" I heard Kaitlyn say quietly.

"Oh, yes. He's done it a couple of times," Joanna replied, also quietly. It was like my subconscious had heard I was being discussed and had woken me up. I continued to act asleep. "The first time he did it was before we fucked for the first time."

Kaitlyn gasped. "You've been fucking?"

Joanna snickered quietly. I thought they were being quiet to not wake me. "For weeks."

"Slut! Why didn't you tell me?"

"Because it was so fun seeing you get bent out of shape. Consider it revenge for all the fashion shows at work."

"Revenge? Did me showing off what I was wearing bother you?"

"Hell yeah! 'See what expensive lingerie my boyfriend bought me this week.' You know I don't have anything like that. All my underwear I buy on sale at Wal-Mart."

"I should have known, Joanna. I'm sorry. Forgive me?"

"Sure. Forgive me?"

Kaitlyn laughed. "Sure. Even?"

"Even."

There was a pause. I started to drift back to sleep but perked up again when Kaitlyn said, "Did it bother you when Brandon kissed on me?"

"No," said Joanna like it was obvious. "It was my suggestion."

"Would you...would you mind if he did it again tonight?"

I had conflicting feelings about kissing and nibbling on my sister. Part of me thought it was wrong, but it was easy to dismiss that as no one else had been upset about me doing it. I had eventually settled on that it was a stupid thing to have done, but I had done stupid things before and would do stupid things again, particularly after a few beers, so there was no point worrying about it.

Joanna asked, "What would Paul think of that?"

"After we had sex last night, he made a joke about me liking my brother kissing on me too much. I'm told him that he'd better hope that Brandon did it again as he wasn't putting me in the mood for sex."

"Ouch!"

Kaitlyn said in an angry hiss, "Yeah." Then her voice cooled. "Paul's not going to do anything that could result in him being cut off." She sighed. "And I don't want to cut him off as it'll ruin the vacation for everyone else. But I can't count on him to put me in the mood. He's not good with foreplay; he always wants to go straight to sex."

"And Brandon kissing on you certainly put you in the mood." Joanna cackled quietly. "So you want to do tonight like we did last night?"

"Yes."

"Last night was fun. I've never done anything like that before, but would enjoy doing it again." Then in a teasing tone, "I'm okay with lending my awesome boyfriend to you for a few minutes."

"Thanks," said Kaitlyn gratefully. After a few moments, she added, "Brandon's been a good boyfriend for you."

"A good mercy boyfriend."

Kaitlyn sighed. "He's not doing anything with you because I've asked him to. He wouldn't make love to you unless he cares for you. He genuinely likes you, Joanna."

"Then why does he always go out with both of us instead of just me?" Because we all have more fun when it's all three of us, and Kaitlyn doesn't mind being a third wheel. "Why didn't he spend more money on me? Take me to nice restaurants? Buy me nice lingerie?" Because I'm a struggling college student working a minimum wage job. "Why did you keep pushing him to make love to me?"

After a long pause, Kaitlyn said in a pained tone, "Brandon doesn't spend lots of money on his girlfriends. He shows his affection in other ways. And you can tell he cares for you in the way he looks at you and pays attention to you. Every girlfriend he's had has enjoyed having him as a lover. I wanted you to have a very positive lovemaking experience." Kaitlyn's tone lightened up. "Am I your best friend or what?"

"You are my best friend," replied Joanna with warmth in her voice. "Have been for years."

The girls moved on to subjects I wasn't interested in. I was angered and frustrated that Joanna still considered me a mercy boyfriend. What did I have to do to convince her that I cared for her? I had been as loving and as affectionate with her as I had been with any other girlfriend. I was suddenly very glad I hadn't said "I love you" last night. She probably would have not returned it, which would have made things very awkward.

* * * *

In the afternoon, we went jet skiing. While Joanna and I were riding a two-person jet ski, she told me about Kaitlyn's request.

I said, "Aren't you bothered by me lightly making out with my sister?"

"No! It was my idea. It was harmless fun. Last night was a lot of harmless but very exciting fun. Kaitlyn and I want to do it again."

I felt it was a stupid thing to do, that we could wind up embarrassed about it. But having a group make-out party twice was no more embarrassing than doing it once. "Okay."

* * * *

After jet skiing, we had a wonderful dinner and enjoyable post-dinner conversation. When Mom and Dad left, Kaitlyn said, "Chairs like last time" before she and Joanna disappeared into her bedroom. I felt apprehensive. Though I had enjoyed last night, I couldn't shake the feeling it had been wrong. I felt like tonight was going to be more wrong since we were sober, and I knew I was going to be lightly making out with my sister in front of my girlfriend and her boyfriend.

Paul said, "I wonder what they'll wear tonight."

I shrugged. I tried to convince myself that seeing Kaitlyn in a bra and panties was just like seeing her in a bikini, but I failed — bra and panties felt forbidden, which made seeing her in them very exciting. Then I shook my head; we were going to have some harmless but exciting fun, just like Joanna said. No one would get angry; nothing to feel embarrassed about.

The door opened and I turned to see the girls come into the room. Joanna led this time, dressed in the same bra and panties as last time.

Paul said, "Nice. My favorites."

Once I got a good look at Kaitlyn, I could see why the bra and panties were his favorite. They were a dark blue which looked great against Kaitlyn's skin. The bra had a circle close to Kaitlyn's neck, a circle beneath her breasts and a clear mesh connecting the two circles that had a plunging 'V' in the middle. The mesh lightly held her breasts, and they shifted noticeable as she walked. The mesh had stars scattered across, two of which strategically covered Kaitlyn's nipples. I could see all of her tits except where the stars were. The panties had an inch-wide ribbon of silk across the top with lace beneath. Right in the middle, the lace was missing and instead there was a deep V that must end just above her pussy. Any doubts whether Kaitlyn shaved were gone. She looked sexy as hell in her outfit. Kaitlyn knew how to strut her stuff, and she oozed sexuality as she sashayed.

When the girls reached the space between Paul and me, they again stopped for a moment before Joanna walked sultrily towards me as Kaitlyn did the same towards Paul. I smiled at Joanna. She did look sexy as she walked towards me, even if she was the moon to Kaitlyn's sun.

I was ready with a kiss when Joanna slipped into my lap. After our first kiss, Joanna moved forward and whispered into my ear, "Lots of kisses tonight" before kissing along my jawline back to my mouth.

I was happy to comply. I loved kissing her. She had soft, full lips that felt great against mine. After a few kisses, I heard Kaitlyn say, "Not yet, Paul". I tilted my head enough so I could look over and I saw Kaitlyn pulling Paul's hands down from her tits. I sympathized with Paul — how could Kaitlyn expect him to keep his hands off her tits when she was wearing that bra?

I pushed Kaitlyn and Paul out of my mind and concentrated on kissing Joanna. We kept kissing on the lips, but in slightly different ways that made the kisses hotter and hotter. Sometimes she'd grab my bottom lip between her lips as I pulled away. Sometimes I did the same to her. Sometimes I'd run my tongue over her lip as soon as the kiss ended. The whole time we were kissing, I kept thinking of Kaitlyn and Paul doing the same thing on the other side of the room. I heard another, "Not yet, Paul", but I was so into kissing Joanna that I didn't look this time. She was more aggressive in her kisses tonight than normal, like kissing in front of Kaitlyn and Paul was getting her extra excited.

I heard Kaitlyn say, "Stay here and, in a little bit, we'll go to our bedroom." I stopped kissing Joanna; she got up and walked towards Paul. I got up too, making room for Kaitlyn to sit down. As soon as she was seated, I kissed her neck. She let out a small gasp and grabbed my hands, pulling them to the bottom of her rib cage. As I did the kissing and nibbling, I moved my hands slowly in circles. To my surprise, Kaitlyn reacted more strongly tonight than she had last night, getting much more into the kisses and nibbles.

While I was kissing along Kaitlyn's shoulder, I looked across the room. Joanna was seated on Paul's lap, and Paul was running his hands up her arms to her exposed shoulders. Joanna gave me a smile. Paul looked bored. I kept kissing along Kaitlyn's shoulder. This time, I kept kissing once I crossed her bra strap and kissed all the way to end of her shoulder. When I was done, I stood up.

Joanna was the one who got up immediately this time. She took a few sensual steps towards me with a big smile on her face before reaching behind her and undoing her bra. She kept her eyes on my face as she peeled the bra off her and tossed it aside. When she reached us, Kaitlyn got out of the chair and left my vision as I stared at Joanna in amazement. Joanna rotated the chair ninety degrees and ordered, "Sit down." I sat down in the chair. Joanna immediately straddled my lap. She grabbed my head in both hands and said loudly, "Suck it!" as she guided my mouth to her tit. Her nipple was already hard before it entered my mouth. I sucked gently as I grabbed Joanna's ass firmly in my hands. This was so fucking insane. Last night had been crazy, but this was even crazier.

I happily sucked on Joanna's tit while squeezing her ass until she pushed back on my head. She guided to me her other tit, and I greedily sucked on it too. Last night had been hot, but tonight was far hotter. I wondered — had tit-sucking been a part of the plan? Something they had decided on while they were in the bedroom changing into bra and panties? Joanna had walked towards me topless with total assurance.

Joanna pushed back on my head and again I let go of her tit. She guided my mouth back to her first tit, and at the same time, shifted towards Paul and Kaitlyn so I could see them easily. Kaitlyn's bra was off and Paul was furiously sucking on the right tit, which was closest to us. I was shocked to see Kaitlyn was red-faced with anger. What was she so angry about? Was the guys frolicking on second base in front of the other couple too much for her? Was Paul doing something that made her angry?

Joanna said loud enough for Paul and Kaitlyn to hear, "Paul said it was boring to watch you kiss on Kaitlyn. He asked me to do something he'd find exciting. Do you find this exciting, Paul?" Paul nodded his head vigorously while continuing to suck on Kaitlyn's tit. Joanna laughed. She ran her hands through my hair and said quietly to me, "I hope you find this exciting. I find it very exciting."

Joanna twisted my head gently so I was looking at Paul and Kaitlyn again. Anger was gone from Kaitlyn's face and it was replaced by something I couldn't place, but it wasn't pleasure. Paul was sucking on the left tit now, giving me an unobstructed side view of the right one. I had known my sister was well-endowed, but it still shocked me to see exactly how well-endowed she was, how proudly her tit stood out on her chest. Her areola was a light brown and looked larger than average in size. Her nipple was completely erect.

Joanna said quietly to me, "I think Kaitlyn wants you to look at her tits. I bet it's making her very excited. I'm sure she's jealous that you're sucking on my tits instead of hers." Joanna added gleefully, "I love making her jealous."

After I had suckled on Joanna for a bit, I couldn't resist looking back over at Kaitlyn and Paul. Paul was mouthing her left tit again while Kaitlyn was looking at me. We locked gazes. As we continued to stare at each other, I saw out of the corner of my eye Paul bringing up his hand to Kaitlyn's near tit. He started playing with the nipple, running his finger around it and tweaking it. It was like he was showing it off to me. The whole time, Kaitlyn moaned as lust filled her face.

Joanna said loudly, "What are you going to do tonight to your naughty girl, Brandon? Are you going to give me a hard fucking?" Hell yes! An odd look came over Kaitlyn's face. "How are you going to fuck me? Doggie-style? Doggie-style on the couch?" I didn't care where or how we fucked so long as we fucked. I had never wanted to fuck so badly in all my life. I couldn't wait to get my cock in Joanna's pussy. The odd look on Kaitlyn's face became one of longing. "How about you throw me over the arm of the couch and take me there? Would you like to do that?" Kaitlyn appeared to whimper, like she wanted me to throw her instead of Joanna over the arm of the couch and fuck her.

Kaitlyn pulled Paul off her tit. She jumped off the chair so she was facing Joanna and me, giving me a good look at her tits. Joanna got up and faced Paul and Kaitlyn. Kaitlyn grabbed Paul's hand as she said, "Let's go!" and pulled him towards the bedroom. Paul took a good look at Joanna's tits before running off. We watched them cross the room to the bedroom and slam the door.

Once the door was closed, Joanna pulled off her panties. She walked quickly towards the couch and lay face down over the arm. "Fuck me, Brandon."

I was right behind her. I pulled off my shorts and quickly guided my cock into her hole. As she was bent way forward over the couch arm, her ass was way high in the air. As I made my initial push, I discovered Joanna was already very wet. I pulled back and then pushed my cock all the way in.

"Oh yes!" hissed Joanna. After I pulled back again, I slammed into her. "That's it! Fuck your naughty girl." I did, my body slapping loudly against hers each time I thrust into her.

"Oh, yes. I've been so naughty," Joanna mumbled into the couch.

"Does my naughty girl want a good, hard fucking?"

"Oh, yeah! Fuck me, Brandon. I want it bad."

I gave Joanna her wish, fucking her as hard as I could. The first time I had called her naughty, it had been just another way of teasing her, but I had known then that she liked being called naughty. Tonight, she had taken naughty to a whole new level, and I could tell she had found it very exciting. It had excited all four of us. I wasn't certain what I thought about Joanna enjoying being naughty, but I was too focused on fucking her silly to give it much thought.

It wasn't long before I could feel myself cumming. "Here it comes, my naughty girl."

"Give it to me. Give it to your naughty girl."

I pulled back once more before slamming into Joanna, firing a massive load deep into her pussy. I shuddered with pleasure as all of the sexual tension that had built during our joint make-out session was finally released.

It took me a bit to catch my breath. I was sweaty all over. I savored our fuck for a while before saying, "That was awesome, Joanna."

Joanna looked back at me and gave me a big smile. "I loved it too."

Joanna reached over to a towel on the coffee table and did her best to throw it to me. I pulled out and used the towel to absorb our juices. Joanna moved off the couch while holding the towel and pointed for me to sit down on the couch. I had a good idea of what she wanted, so I sat down on the edge. Joanna lay down with her head in my lap. She let the towel drop, exposing her pussy. "Now make me cum."

As I reached my hand towards her pussy, the thumps of Paul and Kaitlyn fucking started, with Kaitlyn moaning in time.

Joanna said, "Make me cum with your sister."

I slid my finger between her pussy lips and rubbed against her clit. Joanna hissed. I rubbed some more, and she was panting. She soon matched her pants with Kaitlyn's moans. I again had the feeling that I was making Kaitlyn moan as I fingered Joanna.

Joanna came before they finished fucking. After she caught her breath, she said, "Let's fuck in our bedroom."

We fucked with Joanna on top. The whole time we fucked, she'd occasionally mutter, "Fuck your naughty girl."

* * *

The next morning, Tuesday, I was awakened by Joanna amorously snuggling on me. Based upon the amount of light in the room, I'd guess we had fifteen to thirty minutes before Mom would knock on our door. Joanna and I couldn't have sex, but we could quietly make out. I tilted her head up with my hand and kissed her. The kiss morphed into a long, smoldering one.

Joanna said, "I had a great time last night. Did you?"

"Yes. It was crazy, but it was also crazy hot. You were incredible, my naughty girl."

Joanna smiled. "So you're not angry at me for being naughty?"

"No."

Joanna moved in for another kiss, which turned into another long, smoldering one. Joanna stroked my morning wood, making it even harder.

I said, "This is making me want to pee."

Joanna snorted. "Then go pee." She added sultrily, "I'll be lying naked on your bed when you get back." Joanna wore only panties when she slept with me, which meant she'd strip them off while I was gone.

I pulled on some shorts, went to bathroom and came back. During my walk, I decided to discuss something with Joanna that was bothering me.

When I got back in the bedroom, the covers on the bed were thrown back and Joanna was lying naked on her back on a t-shirt. She wiggled her finger at me in a come here gesture. As I slid into bed next to her, I said, "Let's talk for a bit."

Joanna stretched sensuously like a cat and said, "Okay". She grabbed my hand and pulled it towards her pussy. "Talk."

"Do you think we crossed a line last night we shouldn't have? It was one thing for us to kiss and grope in front of each other, but having the guys suck on tits is quite another." Particularly as I had watched my own sister getting her tits sucked.

Joanna maneuvered my index finger between her pussy lips and pushed up against it as she said, "It was a lot of fun, no one got angry or jealous, and all of us were hot and horny when we were done. I want to do it more. I think Paul and Kaitlyn want to do it more."

"Paul got to see your tits." I wasn't exactly jealous, but I would have preferred to keep Joanna's charms to myself.

"That was the point. He wanted me to make things more exciting, and I did by letting him watch us. Was it exciting for you to see Kaitlyn's tits?"
I struggled for an answer before getting distracted by Joanna moving her hips up and down, causing my finger to slide between her pussy lips. "Joanna," I said disapprovingly. She knew the rule about no-sex while my parents were around.

Joanna gave me a sexy smile. "I'll be quiet. I'm always quiet." She chuckled. "Unlike your sister."

I gave in. I lightly pressed down with my finger, stimulating the area around Joanna's clit.

Joanna said sultrily, "Was it exciting for you to see Kaitlyn's tits?"

Again, I said disapprovingly, "Joanna."

"Brandon, I won't judge you for your answer. Tonight, I want to do something like we did last night, and I want feedback as to what worked for you. Was it exciting for you to see Kaitlyn's tits?"

"Yes." I had loved seeing Kaitlyn's tits. They were the most beautiful ones I had ever seen — just the right shape and size; wonderful skin; her areola were the right shape and color; the way they sat proudly on her chest. I was uncomfortable with how much I had enjoyed seeing them.

Joanna asked, "Did you mind my sharing you with Kaitlyn?"

"No." I had enjoyed it.

Joanna was pushing hard against my finger now and her breath was getting ragged. She said, "Good. I think my sharing makes her even more jealous." She went back to breathing deeply. I worked her clit as she liked, pushing her closer and closer. The only sound was Joanna's breaths — she didn't moan or say anything. I surveyed Joanna as I pushed her closer to the edge; she was a beautiful, fun, sexy, naughty girl who knew how to make sex incredibly hot, and I was lucky to have her as my girlfriend. I moved my finger faster and faster, pushing her higher and higher. After a few minutes, Joanna clamped down on my hand with her thighs as she quietly came. Seeing her cum filled me with happiness.

Joanna pulled me to her. As she kissed me, she wrapped her hand around my dick. We kissed quietly yet passionately as she stroked me. She broke off the kisses and shifted to take my cock into her mouth when there was a knock on the door. Joanna gave my cock a quick kiss on its head and said, "I'll make it up to you later."

* * * *

Over breakfast, Kaitlyn suggested we go jet skiing this morning, and everyone else agreed. The cabin had two of the small one-person jet skis that you stood up on and two of the larger, two-person jet skis that you sat down on. After breakfast, Mom and Dad led the way down to the boat house where the jet skis were stored. Kaitlyn and I were right behind them, and the four of us were talking about what parts of the lake to avoid. When we got to the boat house, I turned and saw that Joanna and Paul were well behind us. They were engrossed in conversation as they slowly walked towards us. I had a bad feeling about them talking that way.

Kaitlyn said to me, "What do you want to start on?" I had turned to face Kaitlyn. "A small one or a big one? I think we should rotate the different jet skis among us so everybody gets a turn driving each type."

I didn't answer as I was distracted by Kaitlyn's bikini top — it was kind of a cross between the traditional bikini top and a crop top shirt. There was something about how Kaitlyn's tits pushed out their covering that emphasized their size. At the top center of her top was a peek-a-boo hole which gave me an enticing view of the top of Kaitlyn's tits.

Kaitlyn said, "What do you think of my top? It's new. I love how it feels and how it holds the girls in place." Kaitlyn shook her tits at me. It took every bit of restraint to keep my jaw from hitting the ground. "See? They barely moved."

I stood stunned for I don't know how long. I snapped out of it when Dad drove one of the big jet skis around to where we were and yelled, "Come on, kids. Let's go!"

* * * *

We spent the morning jet skiing, and all had a blast. We kept somewhat together, the two couples on the big jet skis regularly racing against each other, and the two people on the small jet skis doing likewise.

At one point, Joanna was driving a big jet ski while I held on to her. I asked her, "What were you and Paul talking about on the way to the boat house?"

"He thanked me for making last night exciting for him. And he asked me to arrange with Kaitlyn to do something similar tonight."

She seemed defensive, which annoyed me. Finally, I shook it off; I was making a mountain out of a molehill.

* * * *

After lunch, Kaitlyn, Joanna and I went to the chaise lounges while Paul headed to the hammock. The girls were wearing tiny bikinis, the same ones they had been wearing yesterday. Seeing them wearing so little was affecting me more today. After I had put sunscreen on Joanna's back, Kaitlyn said, "Would you please put sunscreen on mine? Paul's busy."

"I'll spray it on you."

"No one brought the spray," said Kaitlyn. "All we've got is lotion."

I had never applied sunscreen lotion to Kaitlyn before. I looked up at the hammock, and Paul was completely focused on his tablet. I glanced at Joanna, and she was already lying down with her eyes closed. Why not?

I squirted some of the sunscreen on to my hands and applied it to Kaitlyn's back. She pressed lightly back into my hands as I did so. Her skin felt so good and looked flawless. I was glad no one was looking at me, because I had a massive hard on. I applied the sunscreen as quickly as I could and when I was done, Kaitlyn said thanks. I arranged myself the best I could and lay down next to them.

The three of us chatted for a little bit about how much fun the morning had been, and then Kaitlyn dropped a bombshell — "I'm thinking of breaking up with Paul when the week's over."

"You are?" I said. I discreetly looked up at Paul. There was no sign he had heard his name.

"Yeah. He's a great guy and I've loved dating him, but he drives me crazy at times. Last night was kind of the last straw."

My emotions churned in confusion. I couldn't tell if I was disappointed, sad or happy that Kaitlyn was so close to breaking up. She hadn't announced she was definitely breaking up with Paul, so I interpreted her comment as a request for us to try to talk her out of it.

Joanna said, "Are you talking about him going for your tits while you were kissing?"

"No, though I was annoyed that I had to tell him twice to stop. This is probably TMI, but Paul is unimaginative about sex. When we're alone, he wants me to go down on him, then he does oral on me, followed by us fucking. He's good at oral — he always makes me cum — and he's a good fuck, but I'm tired of it being always the same. Last night, I wanted to skip the blowjob and go straight to him eating me out. I was ready to cum right away and fuck. But no — I had to blow him first."

This was TMI, and I was a little shocked that Kaitlyn would graphically describe her sex life with Paul. But it was obviously bothering her.

Kaitlyn continued, "Paul is so different than any other guy I've dated. I've never had a guy shower me with gifts. And I loved it at first. I loved all the sexy clothes he bought me; I loved going to the expensive restaurants. But now monotony has set in. It's the same kind of gifts and the same kind of sex. My god, my closet is full of sexy dresses and expensive lingerie! I actually prefer it now when he sends a card." Kaitlyn was in the middle and turned towards Joanna. "I think that's why I put on the fashion shows at work; to get me excited about the latest lingerie Paul had sent me. I'm sorry it offended you."

"Forget it. I've already forgiven you."

"You're the best, Joanna," said Kaitlyn. "But back to Paul — he's also too eager to have sex when we're alone. I kiss him and he starts pawing at my tits, just like he did last night. It was nice that I got him to slow down for a while. Last night's foreplay really had me fired up and I was so ready to fuck when we went to our bedroom." She paused for a moment. Picturing my sister being fired up to fuck made my head spin. "By the way, Paul wants the couch tonight." Joanna lightly laughed. "He somehow seems to have gotten the idea of fucking me over the arm of the couch." Joanna laughed some more.

The three of us were quiet for a little bit. I tried to process how I felt about Kaitlyn breaking up with Paul, but I kept coming back to Kaitlyn being fired up from last night's foreplay. A big part of the foreplay was me kissing and nibbling on her neck, and us locking eyes during the tit sucking. Was that what had gotten her so fired up? Was she trying to tell Joanna or me that her I-don't-know-what-to-call-it with me had gotten her so hot? The possibilities made my head swim.

Joanna finally said, "What if Paul learned to slow down? Would that make a difference?"

Kaitlyn shrugged. "Possibly. If he learned to slow down, I might be willing to keep going. And if he learned to be more creative. Like I said, he's a considerate, caring guy. Why? Do you have an idea?"

"Somewhat. But first — no bra and panties tonight. I'm tired of wearing a bra which is too big for me and makes my tits look tiny." Joanna turned to me. "Brandon, go jet ski. Kaitlyn and I need to have a serious girl talk."

* * * *

After lunch, we went skiing. When we got on the ski boat, Kaitlyn surprised me by sitting down next to me, forcing Joanna to sit next to Paul. It was far easier with all the noise to talk to the person next to you, so I talked with Kaitlyn. She was in great mood, smiling a lot and laughing easily. Her "girl talk" with Joanna must have gone well. I kept an eye on Joanna and Paul while they talked. Paul was nodding his head a lot and occasionally would have a huge grin. I guessed their conversation was a part of whatever plan Joanna and Kaitlyn had come up with.

At one point, I asked Kaitlyn, "So what do you and Joanna have planned for tonight?"

She gave me a nervous smile. "Joanna wants it to be a surprise. It'll be fun. Go along with it, please?"

"What if I don't?"

"It depends on Paul. He's looking forward to having another night like last night. He told me so on the way to the ski boat. I don't know how he'll handle the disappointment of just being with me. Nothing could happen. Literally nothing could happen in our bedroom." The way Kaitlyn said it, I pictured them spending the night on opposite sides of the room, staring icily at each other. "Or we could have a big fight and break up."

"Are you that close to breaking up?"

"We were the first night here. Since we started having our little parties, we've pulled back from that brink."

I was torn. Last night, we had moved beyond what I was comfortable with, and I felt like tonight we'd keep moving past that line. I could say no, take Joanna into our bedroom, and everything might turn out fine. Or Kaitlyn and Paul could have a big fight, and we'd have a very ugly situation on all our hands. I decided it wasn't worth the risk. "Okay. I'll go along."

* * * *

When we got back to the lake house, Dad and I started working on dinner while Paul lolled on the couch with his tablet. As Dad and I made dinner, I noticed that, while Mom was showering, the girls went to Kaitlyn's bedroom and closed the door.

When Mom and Dad left, the girls disappeared into Kaitlyn's bedroom as I expected. Paul and I moved our chairs into their usual spots. Paul rubbed his hands in anticipation, so he must have had some idea of what was coming.

The door opened, and Paul and I turned to look at the girls. They were wearing terry cloth short-shorts and t-shirts they had cut off so we could see the bottom inch of their tits. As they walked, I was mesmerized by the sight of Kaitlyn's tits as they wobbled. Her t-shirt was thin so I could easily make out her nipple pressing against the material.

Kaitlyn was in the lead, and she stopped in the usual spot. When Joanna caught up to her, I was stunned to see Kaitlyn turn towards me. My eyes were wide in disbelief as she crossed the distance to me. She straddled my lap on the chair just like Joanna had always done. She said softly, "Joanna is going to teach Paul to keep his hands off her tits," and then her lips were descending towards mine. They seemed to move in slow motion for the last few inches. Did I want to kiss my sister? Should I stop her? I was frozen in place as her lips brushed mine. Electricity shot through me like I had been zapped by ten thousand volts. My heart was pounding in my chest. Kaitlyn had kissed me! The next kiss was a solid plant on my lips. Her lips felt so soft on mine. The kiss, combined with her sexy outfit, was intoxicating. I offered no resistance as Kaitlyn kissed me again and again.

I started kissing back. Passion rose within me as the surprise wore off, and I got into kissing Kaitlyn. She was beautiful, fun, sexy and smart. I had never thought about kissing her, but now I realized how much I had wanted to. Our kisses got steadily longer and more playful, with our lips grabbing and pulling. My hands moved up and down her smooth back, caressing her firm muscles. I stuck out my tongue and licked her lip. Kaitlyn pulled back, shook her head no before coming forward for another kiss. I took it the rules for this part was no tongue in our kisses.

I don't know how long we kissed, but it seemed like an eternity. Each kiss was an experience I savored. As soon as a kiss ended, I replayed it over in my mind in the fraction of the second before the next kiss started.

I heard Joanna say, "You've been a good boy," and Kaitlyn stopped kissing me. I felt dazed, like the experience of kissing my sister was more than I could process. Kaitlyn smiled at me, turned and walked over to Paul, passing Joanna on the way.

As soon as Joanna was in my lap, she kissed me hard and pushed her tongue into my mouth. I quickly responded. Kissing Joanna wasn't new and exciting-because-it's-taboo like kissing Kaitlyn was, but Joanna made it hot by kissing me with such passion. My heart continued to pound. Joanna grabbed my hands which were on her back like they had been with Kaitlyn and she pushed them down. I dropped them down to her ass and squeezed; Joanna was wearing no panties. Joanna responded by rubbing her tits against my chest. We kissed lots of different ways, sometimes with tongue and sometimes not but always frantically, like our kisses couldn't fully express our excitement for each other.

Eventually, I heard Kaitlyn say, "Switch back." Joanna hopped off my lap while continuing our last French kiss as she slowly pulled away. During our last kiss, I heard Kaitlyn say, "You were a very good boy." When Joanna broke off our last kiss, she headed towards Paul, and Kaitlyn was almost back to me. She said, "Neck nibbles."

I got up, and Kaitlyn sat down. I kissed her neck lightly, and she moaned. Again, she really got into my kisses and nibbles, moving to give me better access and then melting and moaning as I used my mouth on her skin. I felt like our kissing earlier had her more fired up for this than she had been last night. As I kissed and nibbled, I struggled with how much Kaitlyn and I were enjoying this; I knew we shouldn't be enjoying this as much as we were, but everyone else was fine with it so I didn't see any reason to hold back. But the internal struggle left me feeling dazed.

I kissed and nibbled my way down Kaitlyn's neck and towards her shoulder. I had to pull the shirt collar to the side to access her shoulder. I was so damn horny, and couldn't wait to fuck Joanna silly. When I had kissed all of Kaitlyn's shoulder that I could reach, I looked over at Paul and Joanna. Joanna was lolled against Paul with her head resting on his shoulder. Paul's hands were lightly stroking her stomach. I realized then that with the crop top, Paul could have easily felt Joanna's tits while I was busy with Kaitlyn.

Joanna jumped up and held out her hand. "Come on, Brandon. They've got the couch tonight."

Sex with Joanna was incredibly hot as both of us were so fired up. It was like a wrestling match except we were co-joined in the middle. When we were done, I was physically and emotionally spent.