Oldanon heard on the grapevine back in the closeted days that most homosexual men had very young sisters (or young girl cousins). The story went that they could only be turned on by forbidden fruit.
As they, and their young sisters and cousins, got older, their availability of young female children dried up, they decided, or rather, circumstances dictated, that they take the lower alternative of forbidden fruit, they had sex with other men.
Of course, it's the forbidden fruit. Young girls, and, as they spent years of sex with men, they, of course, put young boys in the mix as well.