Depends on what you mean about "good nuclear families". I mean, much of this isn't scientific (because they won't research it), but even if there's no overt abuse, you can usually find the reason. The mostly "good" family (in social work/psychology known as "good enough" parenting), where there's two sons: one's the athlete, all-star, coordinated, etc., and one is not. Which one does dad pay more attention to, and give more esteem to? If the other one feels rejected by dad, sometimes that one ends up gay. But not always.