The messiest polycule breakup / explosion was a bunch of autistic IT workers around the DC area. Sub Dom drama plus one dude fucked his pesudo-girlfriends sister.
I'd just got back from working overseas and was renting a room in their house. Just kinda watching the whole thing burn. While getting back to normal.
If he's poly and and she's poly and everyone knew everything, is it still awful of him to have sex with her sister? Seems like it's OK if it's OK with everyone, even if other people find it gross?
I know of very very few poly people who would be okay with that. And even if they were, poly requires open communication, and he did it behind her back (which we know she wasn't okay with it because it ended their relationship). So a double whammy.
Highly recommend the book Opening Up to understand how many different types of poly there are and what they might look like.
Sorry, I didn't mean to cause offence at all, I just assumed that in a poly relationships the boundaries were open for negotiation, and that like you say open communication would be key. I didn't know he went behind her back, I know nothing about this story other than what I read on this thread.
I get that in a conventional relationship, leaving someone for their best friend or their sibling would be a particularly heinous betrayal, but didn't assume that that would be the same for someone in a poly relationship. I didn't mean to offend anyone by asking and I apologise for any and all offence caused.
I get that and I appreciate how respectful you're being. I think we can tell by the subtext that it wasn't okay to sleep with her sister (they broke up over this, after all)... and also that is kinda soft incest (to share a sex partner between siblings) so majority of poly people in the west would really not be okay with it due to social norms.