Question

How to identify gay child from body parts?

Answer 1

You don't come to know by looking at someone's body part if they're bisexual or not. While there are some people who opt for changing their genders by surgery or whatever legal methods, all this is mental. You come to know if someone's bisexual or not by looking at their behavioral patterns. Some men and women are attracted to some men and women respectively. There's no term called "GAY CHILD".  Only after the adolescence phase does one realize if they're into women or men or both.
 
I seriously don't know why'd you'd ask such a question. But  idc because I'm getting my points.