I have 5 gay cousins (all on my mother's side). Birth order:
1. younger of 2 boys, older is str8
2. middle, older brother (we think) str8 (KIA Vietnam), younger sister lesbian
3. oldest of 2 boys, younger is str8
4. oldest; younger sister str8[/quote]
I think the cousin thing is more significant than the sibling thing. Why?
I have one cousin who is gay on my mother's side.
I have one (gay) double first cousin-once removed, who is an only child, on my father's side.
I also believe the numbers may be larger than I know because of homophobia in the family.
Genetics is a crap shoot. With smaller families now, it is going to be less likely that we will be able to look at birth order, so we have to look to the "extended" family.
Supposedly, the gene is passed by the mother. That means that in a large family of say six children with three girls and three boys, when the girls marry and have children, they would have the gene from their mother and be able to pass it on to their male children, where it could not be further passed on. My gay cousin on my Mother's side is the child of her sister. Mother had one brother who had a daughter (straight). On my father's side, his double first cousin was a male, so it could be coincidence that my cousin is getting his gay gene from another line.
So maybe we should ask the question: If you have gay cousins, is their mother your mother's sister? If the majority answer yes, maybe there is a correlation there.