If not genetic, then environmental? Such as young boys playing with dolls?
People should look into the number of gay men who grew up without a father or father figure in the home. Nurture is a very strong factor, especially in gay men. Most are very close to their mothers even if there is a father in the home.
Homosexuality is an extreme narcissistic personality disorder usually caused by being sexually molested at a young age and/or being in a dysfunctional family with an emotionally distant father and a domineering mother.