She's trying to push gender roles on him too much, it's not his fault she has a complex. he's also kind of rude I think but that doesn't mean she can be that way.
the sister definitely thinks: 1) its weird and-or 2) rio is more cuter than her and she doesnt like it. LET HIM WEAR WHAT HE WANTS >:( ur his sis, u should be supportive. fuck what other ppl thinks and says, be free and enjoy what u love! go rio~ ur so handsome and beautiful, so confident too <3