11. The Good Buddy
I dated this girl a few years back, and I became really good friends with her brother just because he appreciated my help during a difficult time for their family (their father had abruptly passed away).
2 years into the relationship, the brother contacted me and asked to meet up for coffee and a serious conversation.
Apparently, HE caught his own sister with another guy (a mutual friend of ours), and this crap had been going on for like a year.
As soon as he found out, I was told.
Broke up with her. Still friends with her brother. Go figure.