Love triangles

I just found out a good friend of mine is sleeping with an ex-fling of mine. I met her at a party last year. She was my lover for six months, and since that ended, we have seen each other every few weeks socially - we'd make out and occasionally have sex. Throughout all this, my friend was generally my wingman and would hang out with us, so he knew the girl pretty well. He was always the nice guy, while I was always the more exciting bad boy. I didn't think she or her friends were interested in him at all.

I last hooked up with this girl three weeks ago at a bar - nothing too serious. I found out today from my friend that he had been sleeping with her for the last two weeks and he wanted to let me know. It was a nice, stand-up move. I appreciated it, but I couldn't help but feel a bit sick about the whole thing.

I never had a future with the girl - she knew we were never exclusive and I was with other women on the side the entire time. I wasn't cheating certainly - there was nothing to cheat on, but I mean to say she was never my significant other. I even told her straight up that there was no chance for a future between us and I was just taking the days as they came. Despite this, I can't help but feel like they did the wrong thing by hooking up with each other. I do not have any reason to be upset - any logical reason that is. She was never my girlfriend - I had other lovers on the side, but I can't help but feel slighted. How hypocritical I am.

Is it right for a guy to hook up with a girl his friend had been seeing for a while? Is it right for the girl to do that to someone's best friend? I even saw her yesterday, as friends, just chatting, and she never mentioned it. I kissed her a few times, she never objected. I have no problem with her hooking up with other people, but for it to be my friend (who I never imagined would be able to hook up with her in a thousand years) makes it that much worse.

This post doesn't have much of a point - I just felt confused and wanted to get it off my chest.

I agree nothing was done wrong at face value. It wasn't completely random sex - just because you are not exclusive with someone does not mean you do not have an emotional relationship with them.

I think that while it was logically a legal move, these kind of things always end up hurting friendships between guys. I've seen it happen to many of my friends, unfortunately, and hope to avoid it here, but I can't help but see them both in a different light.

I'm going to bang your wife.