Most Helpful Guy
That happened to me, a few months ago, just with the difference that my best friend was into my sister, but what I did was to keep my friendship apart from their relationship, I mean, I tried to no get involved in that, of course if he do something to my sister I would kill him, but I know him I know he is a good guy for her, even of they break up, I would still be his friend, just don't want to get involved in any drama or anything trivial between them
Most Helpful Girl
My best friend dates my brother and it works just fine. We sometimes go on double date with my boyfriend and it's really fun.