I would be willing to believe that there are environmental factors as a possibility. Yes, as far as genetics goes, we have no way of predicting who is homosexual prior to their official “coming out” about it.
However, it is possible that certain chemical substances can influence from early life or childhood. Either way, I would agree with anyone who does say that there is a difference between committing an act and same-gender attraction.
There are 10's of thousands of ex-gays. How could they get free if it was biological? It is not an immutable characteristic, it is a mental disease.