Why do have the feeling that his father is gayy

You’re not alone

If he’s gay why would he have sex with a woman

Someone can have a kid then figure out their sexuality and finding themselves or could be bi/pansexual as well there's options.

Well that's a common mistake in a country where homosexuality is erased / illegal or never talked about or frowned upon. It's called amato-normativity or also internalized homophobia, you know ? Some people never ever come accross the very notion that being homoromantic/homosexual exist, so if they feel they have '' a little inclination towards something like that '' they just suppress it hoping it will go away and try and ''be normal '' so yes they do have '' sex with a woman once '' , and then wonder why it doesn't work to make a happy marriage. (But sometimes they can find a soulmate in a woman, still are gay, but if the woman is happy with very little sex life then maybe it can work)? (But not very common.)
Also some people are what is called '' demi sexual '' so they rarely feel '' sexual '' at all and more oriented towards emotionnal/spiritual connexion before they can find out if they are '' a little gay '' or '' gay only '' but that's another topic.

Also there are some country where everybody isn't free to get married or not : every young adult is led and pushed towards
< heterosexual marriage > and < having kids >, whether they want it or not, and it's a given that the couple doesn't have sex before marriage (because not so long ago there was no contraceptive so it was for safety and for the sake of the future children, first, marriage, then and only then, make children.) _ that means two virgins would get married and then :-D find out about sex and things like ,
that they are asexual or homosexual without even knowing that it is a possibility, and that there are other people who feel that way. SO there you have it ! Yes homosexual people sometimes , accidentally have sex with the opposite gender, and are even trapped in a heterosexual marriage :,-(