For the hijras, parental control doesn't seem to come into it. If anything, the one most extensively interviewed in that film got himself castrated as an act of rebellion.

Upstairs (where I can't get at it just now) I have a book "The Human Testis and its Diseases" which as a chapter on castration. It describes one of the Russian Skoptsy whose father converted as an adult.   Dad had a special treat for him on his his fifteenth birthday. (I have never read that the Skoptsy ever sang - probably regarded it as sinful).