What do you think is the truth?

A group of me and some good friends went out and drank a ton. At the end of the night we went back to one of our friends house to sleep. Anyways me and a friend caught our two guy friends what it looked like kissing.. one of the guys has a girlfriend. When we brought it up to one of the guys the next day one of them said he thought it was his girlfriend kissing him. We didn’t get around to talking to the single one. My theory is at least one of them is gay… it’s hard to believe they just both were too drunk they were making out with each other? ALSO I’m friends with the girlfriend and don’t know if I should tell her.