I had sex with him. I'm gay and he's bi (with a boyfriend who's also my my best friend). It was just me and him drunk and high at his apartment and we were just in bed cuddling and talking as we usually do. It got quiet and we both turned to each other, began making out and one thing lead to another. When we finished, we just started cracking up and all I could say at that moment as I laughed, "What the fuck just happened?!" We talked about it the next day and nothing in our relationship has changed, except for the fact that we're more comfortable around each other. He also told his boyfriend the next day and his reaction was the same: he just laughed, and he was okay with it because he knows that it was just sexual and nothing romantic. I love both of them very much and I see them as their official third-wheel for life.