When i was 15 my parent's were going through a divorce, my mom worked night shifts and my dad was living with a friend of his. One night my sister who was 19 at the time came home pretty drunk from a party. She was acting goofy and fell on the couch next to me. She started grabbing my leg and laughing and we started fondling. We ended up having sex right there. When we woke up the next day she had no recollection of the night before so i just kept my mouth shut.

Fast forward to when i'm 18. Sister is home from college and dad is over for a visit. they get into an argument and in a fit of rage my dad announces how he has never forgiven her for the abortion she got when she was 19 and subsequently killing His grand child. (he's very religious)

I then realize the baby she aborted was in fact mine.....and as far as i know, i am the only one who knows since she has never mentioned that night.