Originally Posted by SayYes
It seems like this might be an unpopular opinion, but I've always imagined that many people who cheat *are* wrestling with the fact that they're poly.
I have heard of several poly relationships starting out from an affair. However, I have seen cheating done in open relationships as well. One of the first couples I met who were somewhere on the swinger/poly spectrum had a very open relationship. Their only rule was the other person had to be informed before or after if they were going to have sex with someone. The wife told me she caught her husband sneaking around to have sex and tried to hide it from her. He just kind of got off on the cheating aspect of it all. Being honest about it made it less exciting to him.