[dnu]

In case of homosexuality it could be that the genes which cause this in a man are also helping his sister in becoming more attractive to other men (and the brother of a homosexual woman to be more attractive to other women).

I have no stats on this, but it would be interesting to see if the sisters of gay men and the brothers of lesbian women do have more kids than the average (for the same education and income levels, of course).

[gte910h]

There is a Italian study that shows mothers of gay men are quite a bit more likely to bear many children than mothers of only hetero children.

Their conclusion is there at least a partial genetic component, likely coding for "Likes to have sex with men" that the gay men just happen to get as a side effect of the very effective gene for women.