I (26F) found out that my boyfriend (27M) was drunk and kissed his best friend (26M) at a party a couple months ago.

Our relationship is pretty great. My boyfriend and I have been dating for 2 years and everything seems to be on the right track. We live together in an apartment, we see each other everyday and still have a great time. He's the only guy I've ever loved and it feels like this is getting serious so I want to marry him in the future.<br><br>He has a best friend group of 4 guys and they've been friends since middle school (they're all 26-27 now). I've known them for about a year now. I'm particularly close to two of them, let's call them Sam and Alex. Alex is a little bit of a ladies man while Sam has a long term girlfriend. <br><br>I'm not really close with the other two friends. One is called Luke and he's a very quiet nerd that I don't have much in common with. But he's a really nice guy and we get along. Then there's this one friend. Let's just call him Michael. He's a very handsome, well built guy that's into working out and is very charming. I've noticed that my boyfriend is particularly close with him. They both seem to talk a lot so I know that they're best friends but Michael is something else. I don't know why, but he's just TOO handsome and charming. When we're hanging out as a group, he always finds ways to talk to me, touch me, sit next to me and smile at me. I started feeling uncomfortable with him this year because I feel like he's flirting with me.<br><br>Anyway. I recently found out through Sam that my boyfriend and Michael got drunk at a party a couple months ago and my boyfriend kissed him. It was a party with a lot of people but it wasn't one of 'those parties'. They were just celebrating a birthday and got really drunk. Sam said that they were making out for a bit and that he stopped it because he felt weird. He didn't tell me whether they stopped because Michael got mad or because my boyfriend got mad but he said he stopped it nonetheless. After that, they just went on like nothing happened. Sam said that he told his girlfriend too and she didn't see anything wrong with it because "drunk kisses don't count" and that it was probably just a joke between two friends.<br><br>I personally do see something wrong with this. I don't think that my boyfriend is gay or anything but the fact that he was able to kiss another guy, let alone his best friend that I'm not very comfortable with, makes me feel uneasy. I feel like I need to talk to him but I don't know how. I'm scared that he'll get mad at Sam for telling me. I'm not sure what to do. Should I ask him? Should I not tell him that I know? Should I just let it go? I would appreciate your advice on what I should do.<br><br>&#x200B;<br><br>EDIT: I feel like a lot of the comments are focusing on the gay aspect. Like "he's clearly gay and in the closet, you should leave etc etc". I don't think that he's gay. It was a drunk kiss. Let's not forget that. I don't think that he's attracted to guys. I just feel weird because I don't know how to feel about the fact that he was able to kiss his best friend without hesitation. I don't think it makes him gay. <br><br>Not to mention that I don't think that being gay is something to be ashamed of. I have no problem with gay people and I don't think that there's anything wrong with being gay. I just said that I don't think that he's gay because of this. <br><br>What I want to do is talk to him. I want to know how he feels about this kiss. I want to know how serious this kiss was and whether he feels bad about it. I want to know whether they've been flirting behind my back. I want to know whether he's still in contact with him. We can't just break up without him knowing why.