I don't think you'll find that's 100% true.If he wasn't sexually attracted to her, why did they keep having sex? They've got two kids, for crying out loud. A man can't have full penetrative sex without sexual arousal, and he can't be sexually aroused by a woman if he's gay.
Gay men don't have sex with heterosexual women, for the simple fact that they're not sexually attracted to women. That's the whole point of being a gay man.
Schoolchild needs to man up, admit he is bi, and decide what he's going to do about it.
In past times it was quite normal for gay men to be married, and even father children, all whilst hiding/repressing their preference for men.
It's hardly a new thing to think of something/someone else during sex