While i dont think it is genetic (twin studies show it is ~20% chance, and some even ~7% chance, among maternal twins), I dont think it is nurture either. I believe it has something to do with the birth environment, ie what the woman is going through at the time of birth.
Anyway as for those videos, most studies show that while kids dont end up gay they do end up with "gay traits". Like kids from a male gay household tend to be more effeminate where as the kids from lesbian households tend to be the reverse. Not that there is inherently anything wrong with that.