It’s the old “My parent is famous and gets lots of attention, how can I get attention?”. Attention whores produce more of the same.
There was a story that a nanny was in the park and Megan Fox’s nanny was there with her three children. Her children were born male, but are supposedly female now. This nanny said all three of them were complaining about having to be female, and the nanny had to “discipline” them into it. So, I don’t think it’s usually the child’s idea.