Forgive me, I’ve tried polyamory but I don’t quite know what counts as “cheating” when the relationship is opened like this.

So my sister (14) “Liz” went out with “Asher” (16) for like a week. Asher was always very giggly, flirty, and romantic with Liz and would find couple songs and say “That’s us!”. My sister seemed very happy with her new boyfriend.

Asher turned out to have a boyfriend he had been dating for a year before Liz. Liz knew about the boyfriend, but since he said “I’m poly and in an open relationship”, we all assumed the boyfriend was okay with it.

Turns out, he wasn’t okay with it and Asher got into a relationship with Liz before telling “BF”. Then, afterwards, he said “Well I like “BF” first and I like him better than you so I’m breaking up with you.”

Maybe I’m too upset because she’s my sister, but kind of a jerk move there on his end.