How do you delete a user of a banned account?

So I have a few users on my PS4. I have an user for friends who come over, a user for my brother, and my main user. However, my brother somehow got himself banned (or suspended, it doesn't specify) and now he can't sign in to his account. I can't delete his user because it says that he needs to be logged in, in order to delete his user. Obviously I can't sign in, and it doesnt let you sign in to another account, so we're kind of stuck with a useless, banned user. How do I go about deleting it? Am I stuck with this user?