100% guaranteed the kid thinks they're kin with anime characters. This is not a real thing.

By which I mean, if you're not familiar with the phenomenon, it is indeed very popular with kids on the internet these days to claim that they are literally multiple fictional characters and that this is DID. It's mainly used to harass other people online for shipping the wrong things or not liking their favorite character. I feel sorry for their parents if they try to take it out of online spaces. They're just dumb kids and should not be taken seriously.