human brains are varied and there's no one single way a family should be structured. Kids need adults who are reliably there, keep them safe and love them, and there's a ton of different forms this can take.
My layperson opinion is that as long as there is at least one male father figure, and one female mother figure, anything is on the table - from polygamy, to diffused-parentality villages.
Anything is fine, again, as long as there is a stably-present parent figure of each sex. With gay marriage, let it be an aunt; grandfather; next-door-neighbor; whatever. But it should be something