Why are you assuming closeted gays have wives? I know I never had a girlfriend when I was closeted (I am an MTF transexual). I also know a few gays that never had girlfriends or boyfriends until after coming out.
They will have sex with there wives so they can stay in the closet.If you know that your husband is gay or bi then you shouldn't be with him. Unless your alright with sharing him and all the diseases that come from that life style.