If your friend/relative decided to change their gender identity and wanted to be recognised as she/he respectively would you have a problem calling them by that?

Brought this issue and discussed it with the kids
Son 11 = uncomfortable with it, to begin with
Daughter 13 = didn't have a prob with it. A girl at their school decided he was a boy, dressed as such, changed his name used the boys loo for a year then school said use girls loo