Ask yourselves --have they found a gene that all gays share? No, they have not --they are more likely to share a gene for poor eyesight or artistic talents or frail body type --nothing that is exclusive to homosexuals.
Is it possible that something occurs in the womb with the mother's hormones that causes sexual ambiguity? Perhaps, but it will show up in their bodies --not just in their heads. So far, homosexuals generally are absolutely like heteros in their hormone levels and physical features.