how do i ask my cousin if he's gay

I KNOW RHIS IS GONNA SOUND LIKE A CLICHE YAOI STORY BUT PLEASE, IT'S THE TRUTH I CANT DO ANYTHING ABT IT. Ok so I have a theory my cousin (24) is gay BUT im not sure. basically whenever i go to his house (which is almost everyday) i ALWAYS see him with his one friend, not multiple JUST one. like i see his friend so often im basically friends with him atp Me and my cousin have a big age gap but we r super close i tell him everything (including super personal stuff like strange sex/relationship stories) and he tells me stuff too but i do NOT have any bit of memory of him saying he slept with a girl or anything like that and honestly IDGAF but ive been thinking recently and realised him and his guy friend i mentioned earlier seem VERY close (theyre not childhood friends or anything but i THINK they met in uni not sure so they might have been friends for a year or two). like i know guys are normally really close and do homo shit with each other and still claim theyre straight but like this was next level. idk if im over-observing things cuz i read alot of yaoi but it seems rlly odd to me idk. Also why im even taking him being a homosexual into consideration is cuz he has NO GF!! and dont think this man is hoeless cuz goddamn this mf's roster is full and constantly increasing but he NEVER flirts back like bro he's got girls who look like the literal human embodiment of the moon in his dms yet he never shows any interest, always yapping with his bum ass best friend so like...how do i ask him if hes gay and dating his 'friend'