As with Simon Levay's earlier work, it looks like your 2nd link (can't find anything in the first link) authors were predisposed to find as they did. In fact, in rahman's study of identical twins, only 35% showed any deviation between the two twins in each set that might
show a genetic connection.
I have never disputed there is a possible genetic predisposition towards preferring the same gender, sexually, but to suggest based on any of the currently available evidence that "gay people are born gay, period" because of the few any of us know personally and have talked to about the subject is not supported and quite foolhardy.
IN my opinion, heterosexuality is hard-wired into us. If one of those wires is frayed AND the environmental factors are "right," then an individual might be attracted to the same gender. IF that person gets older and acts
upon that attraction, THEN they can rightly be called homosexual.