Originally Posted by Purpurea
He will tell her about the cheating next time they meet in May (they have a long-distance relationship). I think though he should tell her sooner, so she can make her own decision if under these circumstances she still wants to travel all the way to see him.
I've been in her shoes before, too. I once was in a long-distance relationship with someone I was crazy about, who had been involved with me in person and then moved away. We corresponded for about two or three months and he was so lovey-dovey toward me. We wanted to see each other again, so I made arrangements to travel, spending money I really shouldn't have. I even delayed starting a new job so I could be with him for a week.
When I got there, he told me he'd been seeing other people, and I was devastated. This was when I wanted only monogamous relationships. Never in his letters to me (yes, these were the days before email), did he indicate that there was anyone beside me that he was interested in. I had my hopes up that it would become serious and perhaps he might be someone I would want to move away for.
Not only was he seeing someone else, but he had slept with quite a few women and hadn't even been using condoms! Thankfully, he informed me of this on the day I arrived and not after a few nights of being sexual (though I always insisted on condoms). I cut my trip short and incurred more cost because the airline charged me for changing my plans.
It was just a mess, but mostly because I felt so betrayed. It is terrible when someone behaves deceptively. But waiting til I made such a long trip to tell me was even more cutting. I felt so dismissed and unimportant to him. He was surprised when I told him, "If I had known, I wouldn't have made the trip." I don't know how he didn't realize that having all the information would allow me to make an informed decision, one of which could be to walk away from the relationship. Somehow, I guess he thought I wanted to be with him no matter what. Pure arrogance on his part.
I know you don't think anything beyond your relationship with this guy is your responsibility, but if I were you I would insist that he tell her before being involved with him again. I just could not live with knowing that the person I am in love with is so uncaring, devious, and dishonest, not to mention what your involvement with him does to her.
I also think that there are probably plenty more people who would be open to a poly lifestyle than you realize, and so it really might not be as difficult as you think to find another boyfriend. But I would encourage you to be open and honest on all fronts and insist on the same personal integrity from your partners. Then you would truly be poly, not just cheating and okay with it.