Was staying with my stepbrother and his fiancé in my mom’s house that they were renting. I was just out of HS and didn’t want move to where the parentals where. All started innocently enough just hanging out. Talking. Never even really thought about her in that way. Then one night I came in late with a case of blue balls and was getting ready for bed and I heard something across the hall. I opened my door and I heard them fucking. Instantly got hard and figure what the hell. As I listened to her moan and the bed squeak I stood in the hall and pleasured myself to her moans. . lol. Fast forward a few months again just some silly flirting and I know I shouldn’t but we are both 18. One night he went to bed and we were flirting and kissing and I was gonna try. I was trying to get it in and it just wasn’t working quite well when we heard the door open and he called out to her. We were on the sofa so we froze for a second and I lept over to the other used the living room dressing while I was in the air. lol. Then one day we are playing around just us at home and she comes and tickles me then runs to my room. I’m like no way so I go in after her and one thing led to another and tickle led to some kissing. Then before I knew it I was sack deep in my soon to be sister in law. Started missionary but she wanted to ride. She says that’s her cum position. She starts riding me and grinding me. Her moans exactly to what I beat off too. As she came she leaned forward onto me and about that time I hurried and pulled out and shot it all over her fat ass. Then went on like nothing. Next day, started early. Fucked in my bed. Then the tub. Then the sofa. Then I was just going in after he left for work and fucking her in their bed. I was a shit I know it. Was also my first BJ and she swallowed. Big fat ass. Smallish tits. Then I told a friend and started telling her and then next thing I know we are both fucking her one night while he slept. Took turns going from pussy yo mouth. Till he came on her stomach and I had her swallow mine. Eventually it all came out and I’m sure he’s thankful for it now but not so much then.