My ex is bi at least. He was caught red handed kissing a bloke, and rubbing his crotch, by my best mate (on a night out with a lot of mutual friends, that my spidey senses told me not to go to, so I pretended to be ill).
I'd been asking him for a long time if he had feelings for men, and he kept denying it. I'd pegged him a few times (per his drunken request) and he took a 6 inch dildo first try 
we'd tried him pentatrating me before, but he could just about squeeze in a pinky finger. I become quite convicted he had to have had regular anal at some point, before this/had clearly been fucked by a man/men. I tried gently asking a few days later, but again, more denial.
The sex was excellent overall, neither of us had any problems coming, but he'd often go off it randomly for long spells. He was never happy in our relationship. He used to walk out a lot/disappear. Would often be in an awful mood for no apparent reason. Accused me when drunk of "trapping" him (with dc), and eventually admitted sober to feeing trapped. He got very depressed and suicidal, attempted it on at least two occassoions, and he became more and more destructive and physically abusive, and ramped up the emotional abuse (picking more and more fights as an excuse to storm out/disappear/"clear his head" etc). I think he was trying to provoke me into ending it and being the bad guy, in which he finally succeeded. He cheated on me with other women (which I couldn't prove at the time, and was nearly driven crazy by his gaslighting and accusing me of being paranoid, but he's since admitted to a lot of things).
When I finally threw him out, I also told everyone why, which he didn't expect. He attacked me two weeks later. It went to court, he got off. I think he's ashamed of himself, and his attraction to men, and felt like I'd outed him. Forgets that he's camp as Christmas, that I was amazed when he first tried it on with me to the point I said "I'm sorry I was convinced you were gay!". I was the first woman in years he'd publicly introduced as his gf, and even his own parents had been speculating for years...
We actually co parent quite well now, a few years on (and I'm glad to be rid of him, and to be able to ask him to leave if he starts to aggrivate me). He still totally denies he's bi/has gay proclivities. I couldn't speak to him for a year, after he seriously assaulted me, and when I realised I'd been nothing more than a beard and "convenient" to him. But I eventually forgave him (mostly for my own sake). He still has tons of issues, and is pretty much a functioning alcoholic, so I feel more pity for him now than anything.