Just realized my 10yo has a YouTube account I don't know about

Found out yesterday that my son has been watching some pretty questionable content on a channel I've never heard of. We use parental controls on the family iPad but apparently he created his own account on a tablet his grandma gave him. I'm not sure if he did anything wrong but now I'm paranoid about what else I don't know about. Time to have some hard conversations about privacy vs safety I guess.