10 years ago, when I was in high school, my adoptive cousin (K) had a girlfriend (L). He was overly controlling and would even put his hands on her—he was a bad person all around. He would mistreat my aunts and get physical with them too; we were raised by women, and women only. So it was kind of a big deal at the time to think he’d turn out like that

I’ve seen him punch L in the face, and honestly I was too scared to ever do anything back then. He would isolate her, and forced her to take the train to and from school with me, because he didn’t want her to have friends. But she secretly remained friends with this one girl (V), who was in the same math class as me and L

One day during class, L got up to throw away some paper, and V said she caught me staring at her ass. Which honestly wasn’t true, but I just laughed it off. At the end of the day, when me and L were taking the train back to our area, she told me that V told her she saw me checking her out. I denied it, but she didn’t believe me and instead told me she was flattered

Fast-forward a month later, and we start hooking up just about every morning. Her friend V was known for sleeping around (which wasn’t a problem with me, but you know how high school kids are), and after L told V that we’d been having sex behind my cousin’s back, she was thrilled. She hated my cousin because of how he treated L—this lead to my first (and only) threesome

I don’t regret it—he was, and still is a piece of shit. I haven’t spoken to K in 10 years. No one’s found out, and I’ve never told anyone this. I’ll probably take this with me to the grave

TL;DR: I have an estranged, abusive (adoptive) cousin. I fucked his girlfriend, and her friend in high school. The friend hated him because of the abuse, so she involved herself in the affair as a (secret) fuck you to him