F***** my girlfriend's sister
This happened last year after my (now ex) girlfriend and I had a massive argument about how much we see each other.
We hadn't seen much of each other the past couple weeks. Then she suddenly wanted to go away on holiday with friends for 10 days but I wanted to spend more time with her.
(I'm not trying to justify what I did, just giving a bit of background info).
That night i ran into her sister at the pub. Bought her a few drinks and chatted for a couple hours. We'd always gotten along very well. Harmless flirting etc. Never thought of her in a sexual way. However that night, probably due to partly the alcohol and mainly my anger towards my ex, we were flirting a little heavier. And the conversation turns to s** and talking about our experiences, fantasies etc.
I eventually ended up taking her home and f****** her most of the night. And then again the next morning after we woke up.
Me and my ex broke up a short while after, just before her holiday. As far as I'm aware, she doesn't know what happened with her little sister. Though I'm pretty sure that if she knew, I'd have heard about it by now