I'm so confused

My girlfriend and I were talking about gay couples in Singapore and our conversation went bizarre when she mentioned a pair of unfriendly gay couple living upstairs.

Me: Just because two guys are sharing a flat doesn’t mean they are gays.

Friend: They are gays. Confirmed.

Me: Well, they could also be bisexual.

Friend: No, they are not. They are straight.

Me: Huh?

Man, I am getting a headache. The world is getting too complicated for me. Just a moment ago I didn’t know a new gay species exists.

In future, when a guy tells me he is straight, do I ask: “You mean you are a straight guy or a straight gay?”