This story may seem like it should be in cheating heart but just hear me out. A few months ago I got married to the love of my life. Now wife's little sister came to stay with us for the wedding because she was the maid of honor. She had just graduated college at 21. The night before the wedding my wife went to stay at her friends house so they could get ready in the morning. Her little sister stayed at our house with me cause there wasn't enough room at the other house. Later that evening I was laying in bed watching a movie when my wife's little sister came in and asked what I was doing.I told her just relaxing and watching tv, she asked if she could join, I figured sure why not. She the jumped into the bed with me and snuggled up close, this wasn't unusual I have been close to her for years and she has cuddled up on the couch with me and my wife many times before.she then turned to me and started asking if I was nervous about tomorrow, I said no I love her sister. She then asked if I was ready for the wedding night, I asked what she meant. She then started rubbing my inner thigh getting closer to my dick and said you know the wedding night sex. She then all of a sudden puts her hand on my dick and starts rubbing and massaging my balls. I ask what she is doing, she replys with i want to make sure you will properly satisfy my sister on her big day. I tell her this is inappropriate but ther was no stopping her. My dick was getting hard as a rock and she said it looks like you want it too. Before I knew it she had my dick out and was sucking it. Now I could have stopped her, she was only 100 lbs, little A cup tits brunette hair, she was beautiful and so sexy that I have thought about what sex would be like with her before. But I didn't stop her because I was paralyzed with pleasure. It felt so good her blowing me like that. She came up and said she always wondered how big my dick was and she said she liked it. Now I am only a boy 7.5 inches but pretty thick. She then stripped completely down revealing her petite body to me for the first time. Her pussy was completely bare and could see her little slit glistening cause she was already wet. She climb on top of me and positioned the head of my dick to her entrance and began lowering herself on to me. Now she was tighter than my now wife so she took a couple min to get used to it but before I knew it she was riding me like a porn star. Oh my god her pussy was so amazing she was moaning and screaming in ecstasy and I felt her pussy get tighter and knew she was having an orgasm she kept riding me as fast as she was. She just kept working my dick until I couldn't take it any more and yelled "I'm gonna cum". She screamed " cum inside me" and I unloaded in her just as she was having another orgasm. She climbed off of me with my cum dripping out of her and went to the bathroom to clean up and she brought me back a towel to wipe up. She played in the bed next to me and kissed me on the lips and said "I think you will satisfy my sister just fine"and " this will be our little secret". Now the next day comes I get married but I'm feeling guilty. At the reception later I'm slow dancing with my wife when she whispers in my ear " how was my sister?" I ask what she meant, she told me she knows we fucked last night and that she was the one that told her to do it as a early wedding present but not to say anything about it.I was in shock, my wife then kisses me and says that her sister is permanently moving in and it is ok if I continue to have sex with her. So in a way I kinda got two wives that day. Sometimes I will be fucking her little sister and my wife will come in and ask why we started without her. I love my wife and her little sister.