I watched this & found it very interesting.
I actually have a younger Brother that is gay, he came out in his teens, & I have an older Half-Sister who is gay as well. There is also another Half-Sister who is straight like myself.
We never had any contact with the Half-Sisters until earlier this year (we have the same Father but different Mother's) but as it turns out she & my younger Brother are very similiar in a lot of ways. They had never met since my Brother was a baby so there isn't any way that she could have had any influence on the way he has turned out, they dress similarly, their taste in music is pretty similar,they even laugh at the same daft jokes that everyone else groans at. There's loads of things, even as far as she teaches the subject that he is doing a degree in. & of course they are both gay lol.
We've all had long discussions on this & the consensus within our family anyway, is that nature really must have some influence on stuff like that because we weren't all brought up together. It has to be in the Genes, at least for some people.
Wow that was hard work .... scuse me being all long-winded lol, I think I got the point out eventually