They were clearly sexually attracted to each other enough to have three kids.
Just because two people have kids with each other doesn't mean they're into each other. Especially in heavily religion afflicted societies it isn't uncommon for homosexual individuals to pursue a hetero relationship out of fear of the consequences. Plus, even if they aren't alibi kids, romantic and sexual attraction aren't the same thing. The two in this example are probably romantically attracted to each other at least, and at that point if one or even both of them are gay, as long as they're in the closet about it their partner wouldn't know, and request sex to fulfill expectations of what a relationship should be like. Plus the obvious explanation of them simply not being consciously aware of the fact that they're gay, and acting according the heteronormative behavior they've been taught in their youth.
