Why does it all have to be so complicated and "conspiracy-theory"?
Few people are 100% hetero- or homo-sexual, most of us are somewhere on a spectrum.
Most men who prefer their sexual partners to be men have had sex with women and enjoyed it, despite it not being "the real thing" for them. My stepfather was gay, and had two children with his ex-wife, and while I don't know the details, he certainly had a sexual relationship with my Mum. The notion of a gay man only being able to get it up for men is as old-fashioned as the idea that all gay men look and act like Mr Humphries.
If TC is gay, it seems obvious that he does not wish this to become common knowledge, perhaps because of his career, or because of his religion or perhaps because, sadly, he cannot himself accept his sexuality and wishes he wasn't gay.
Maybe he just wants to be a heterosexual man with a loving family and children of his own. And he meets a new woman and in the flush of excitement of a new relationship he thinks the sex side is all OK, and he can do this, he can have the heterosexual life. But then as in all relationships, the lust wears off and he discovers that actually his heart is not in it after all.
And then it comes to the time when children are wanted in the marriage. As a lot of us know when TTC, it can take a lot of shagging to achieve a pregnancy. And if a marriage has a sexual problem due to an unacknowledged sexual orientation issue then this is likely to make conception even more difficult.
So, what do you do. How about: meet a new girl, fall in love, get her pregnant as quick as possible before the lust wears off, bob's your uncle!