The Boston Globe newspaper's website has an extensive article on research into what makes people gay. I'm posting this link because its an excellent article and I thought others might be interested in reading it. It's a fairly long piece but worth the time to read. The article starts off with the story of 7-year-old twin boys and the differences in their behavior and interests. One displays more feminine behavior than the other even at this early age, a possible indication of his future sexual orientation. The piece goes on to discuss past and current research on the subject of sexual orientation.
Give this article a read, I think you will find it very informative.