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.
AFAIK, the important thing in polyamory is consent. It looks like the boyfriend didn’t consent, so that seems to be a form of cheating, though it’s possible that it’s an honest mistake - maybe it hasn’t been properly established that they have to tell each other first when they want to date someone new. Though it’s also possible that the relationship wasn’t actually open in the first place, or just not in the way “Asher” said it was.
Bit hard to say who was cheated on without knowing all the facts. Though either way, “Asher” definitely has to figure his shit out before starting to go out with someone.