I originally told my mom I was going to be home early afternoon Friday, so I could see her for a couple of hours before she went to work. She works overnights. I didn't make it. I ended up busy at school, and called and just told her and my step dad I'd be there Saturday morning. She said to drive safe, we talked a bit, and she had to head off to get dinner around, and head into work that night. I told her to let my sister know and step dad know I'd be there early Saturday. Well, after my roommate left late Friday, since it was only about an hour drive, I decided to not stay there. I packed my stuff up for the weekend, and didn't bother telling my folks of the change. I just jumped into the car and headed to the house.

Now when some of you read this, you may get grossed out, disgusted or angry that I let this happen, or was involved in this, but I guess you don't understand. I don't. I'd never seen anything like this before, and I'm almost ashamed to admit it turned me on, made me really horny, and it was something I guess I liked watching, because I'm not a prude, but this isn't something you see every day. So you can say or judge how you want.

When I went home, I walked into the living room and found the light on (which was normal), so I just put my stuff in my bedroom off the living room, and I went looking to see who was home. His car was in the driveway, so I figure he'd possibly fallen asleep, and maybe my little sister was at a friends house, knowing I wasn't coming home until Saturday. I heard something downstairs, and figured maybe he was in the den and had fallen asleep with the TV on. As I walked down the stairs, I was behind the door into the basement den, and I stopped in my tracks, as I saw my step dad standing there in nothing but his boxers and no shirt. And I see my little sister standing there, and looking at him. And then I hear her say to him "Yes. I'm sure. This is what I want. If it wasn't, I wouldn't be here with you" and much to my surprise I guess, and shock, I see him walk up to her, put his arm around her, and start to kiss her. And I'm talking a full on, make out intense hot and heavy kiss. And I realize my sister is in nothing but her underwear and bra. I feel almost disgusted to admit this, but in a sick way, it was a turn on. I'd never seen that kind of shit happen in m life, and I guess I wanted to see what they would do. I stood there, them not having any idea I was even in the same room, as this continued for about 5 minutes. He had his hands all over her. Up and down her bra, up and down her underwear, all over her stomach, on her ass. He was panting and breathing heavy. And when he finally stopped, he stepped back, and he had a massive hard on in his boxers. I could see it from where I stood. She just looked at him and said wow. And he smiled and said well yeah. Wow.

I figured that it was just a bit of playing around, or maybe some hot and heavy making out, but she pulled her bra off by unhooking it. He just stood there. And then she pulled her underwear down. I feel kind of dirty admitting this, but had no idea my little sister had such a hot fucking body. No lie. She looked amazing, and it's not like I'd pay attention to her changing or getting naked or anything. I'm just not into that. But seeing her stand there, well it was kind of different. And to watch my step dad pull his underwear down, and stand there, extremely hard and turned on, I guess I didn't know what to do. I just stood there.

They got into it. And I'm talking got into it. Heavy making out, lots of touching, his hands all over her naked body, and then he got her down on the floor, and started kissing all over her, licking her, sucking on her boobs, and getting her all worked up. I stood there, and actually got wet watching this. I was kind of grossed out, thinking that he's out there fooling around with my little sister, and I'm getting horny, but I couldn't help it. And it's not like she didn't want him to do it. But when I saw him do oral sex on her, holy jesus, I thought I was going to lose it. He performed oral on her for like 20 minutes and I think he made her orgasm like 3 or 4 times. I'd never seen a guy do it like that before.

When he stopped, she just sat up, and they were sitting there for a second kissing. And then I heard her say yes. He got up, and walked over to a dresser in the corner of the den. Dug around for a bit, and to my shock, pulled out condom packages, and came over. I stood there, just not believing what I was seeing. And then watched my teenage sister put a condom on him. It took her a bit, but she finally got it on, and said sorry you gotta use this. I'm not on the pill or anything. And he said that's fine. It's worth it. Believe me.

I stood there and watched them fuck on the floor. She was on her back, and I saw his naked ass, and then I saw him go in her. I stood there and watched the whole thing. It lasted for quite some time, and I knew he was gonna bust, because I heard him say that he was ready, and I heard her say you can go ahead. And then like 3 minutes later, I see him pumping really quick, moaning, and then just like pushed one last time and kind of laid there.

They were laying there for quite some time. I got up off the stairs and went upstairs. I was up in the house for probably 45 minutes before they came up. Both kind of surprised to see me, and pretending that everything was awesome, and everything was normal. Acting like they hadn't just fucked in our basement.

I'm certain this isn't the first time they've done sexual stuff before. And I'm not really sure what to think or how to handle it.