It didn't take long for my sister Katie to get her clothes off. With our parents celebrating their 20th wedding anniversary on a cruise, we had the house to ourselves the entire weekend.

"Let's go swimming. I'm dying to get into the cool water". Well who was I to object to a good naked swim?

Shedding the last piece of clothing, she dove into the water as though her hot ass was on fire. I, on the other hand, eased my way into the pool. I'm one of those people who slowly eases themselves into a pool if I've been out in a hot environment for a while.

Rock hard, I finally made my way into the pool waist deep. As I made my way deeper into the pool, I felt a warm presence on my dick. Looking down, I saw my sister wasting no time in her sexcapades.

I tried to back up back to the edge of the pool to have something to hold onto as my sister engulfed my cock. This girl puzzles me. She doesn't get the best of grades in school, but she paid close attention when I taught her how to suck a dick. At least she'll have a good foundation for a promising future.

As she kept coming up for air, I gave her a look out of anger for getting me close then stopping.

"What?" she asked as though she was clueless.

"Can't you ever finish what you start? Fuck, I was so close each time you came up."

"Well if you catch me, you can punish me." With that, she was off, taking laps around the pool like a fish trying to avoid being eaten. I can't swim that fast, so I waited until she got close enough and grabbed her.

"Oh, you caught me! Now what am I going to do?" It's not a question of what she was going to do. It's more like what I was going to do, and what she was going to take.

"Come here. I've got something for you."

Katie jumped on me as though she was giving me a hug. I pushed her to where she was floating on her back. Pulling her down, my dick made its way into her overly lubricated pussy.

"Mmmm. I knew this was gonna happen. Fuck me big brother."

I had my left arm wrapped around her back for stability, and fondled her perky little tits. The motion of the water from her crazy swimming gave us a hand in getting the fun started. Wave after wave brought me deeper inside her beautiful rosebud.

After the waves subsided, I told her it was time to go in the house. Without any shame, she hops out of the pool, leaving her clothes behind. I was close behind, smacking her ass to hurry her along. The jockeys are the Kentucky Derby had nothing on me getting her ass in gear.

Stopping at the kitchen island, she hopped up and spread her legs as far as they would go.

"Are you up for a snack? My treat!" Bullshit. It would be my treat.

I moved in to taste her sweet cunt. Playing back and forth with her clit, I decided to push my luck, then my finger in her ass. Not getting any indication that she didn't want that, I decided to make it a double.

"Are you hinting at something?" What gave it away sis?

"No, I'm getting something. Two out of three isn't good enough. Where do you want to fuck today?" We've covered a lot of the other rooms in our house before our mom or dad got home from work. Unfortunately, we were running out of places to christen.

"How about the bathroom?"

"Didn't we just get out of water? What's the difference?"

"Because if you do what I think you're going to, I don't want the neighbors thinking you're trying to kill me. Besides, if you do put that thing up my ass, I will be screaming." There's always a way to fix that. I told her to go upstairs and start the water.

Following her up the stairs, I made a quick pit stop at my room to grab some lube I had five fingered the last time I went to the store with my mom. Yep. Today was going to be a great day.

Lucky for me, the lube was water based, allowing me to sneak into the shower pre-lubed. Katie turned toward me and gave me a passionate kiss.

"Please be gentle Matt. I've never done this before."

"Don't worry sis. I'll go slow."

Keeping my promise, I crammed the head of my dick past her tight sphincter. I immediately stopped for her to get use to it. She was breathing a little hard, but I chalked it up to the pain of having her ass stretched for the first time.

"Are you ready for me to go deeper?" I asked sympathetically.

"Go slow, but don't stop until it's all the way in. Then stop. It hurts, but there's a few areas it's hitting that feels good."

Any slower, I would have ruined it for both of us. I was on the verge of emptying my balls right at the entrance. Over the last few years, I've managed to learn a lot of self control in when I cum. But when it came to fucking my beautiful sister, all of that training was severely tested.

I began to slowly pump in and out, making sure I didn't hurt this sweet girl who willing let me violate her asshole.

"Speed up a little. It's starting to feel really good."

I reached around to play with her clit. Making sure I prolonged the experience for both of us, I didn't make direct contact with it, but damn near close to it for her to go nuts.

My speed picked up significantly. Before I realize what I was doing, I was pounding my sister's ass. With my balls flapping against her pussy, I began to focus my attention to what I was doing, leaving Katie to rub her own clit.

"Oh god Matt. Fuck my ass harder. Don't fucking stop!"

I picked up more speed. I hadn't moved that fast in a long time. I started to feel my balls swell.

"Bend over farther Katie. I want to cum in your pussy."

She leaned down and grabbed the edge of the bathtub. Just before I blew my load, I pulled out of her ass and jammed myself into her pussy.

"AHH! Fuck me Matt! Cum in me!! OH FUCK! I'M GONNA CUM!"

I felt her pussy tighten around me. Feeling my incestuous cum making its way up through my dick, I unleashed the fury.

"Oh it feels so good. Matt, your cum is so hot inside me. Fill me up baby."

We both fell to our asses. Katie reached over to turn off the shower and fill the tub. We sat in the tub until the water was ice cold. With Katie occasionally taking my limp dick in her mouth, we decided to take a nap together. Naked of course. I was thankful it was only mid morning. The day was young, we were young and the possibilities for more fun for the day lingered.

As we lay in bed, a thought crossed my mind. I had recently heard my mom and sister talking about her menstrual cycle. Katie had just had her period about a week and a half ago. After what we did today, there's a good chance I just got my sister pregnant.

"What would you do if I got your pregnant? You know, by mistake?" Katie turned and looked at me.

"I'd keep it. It's our baby Matt. Not many kids can say they grew up with two parents who have a love for each other as deep as ours."

She always knew what to say to put my mind at ease. Any fear I had about what I had just done to her went out the window.

"I love you Katie. It would be great if you had my baby."

"I love you too Matt. We'll just have to wait and see what happens. Until then, come here big brother. I want some more of you."

Round two began sooner than I thought it would. God I loved her.