Chances are high that there probably is a account ownership issue going on right now. Especially since this is the second time an account was hacked. Given the email was also compromised really makes me believe the PC is probably also compromised. Definately make sure that is secured first or everything else will be for nothing.
Beyond that unfortunately I am not sure. If your PC is compromised, the hacker probably also has access to what every tickets your brother is trying to put in as well. I am assuming though your brother is including the email address in the tickets, probably putting in those tickets in a state where he can not log in to check the status?
I’m not sure our mods are around, and this is mainly a player driven discussion forum. As a fellow player I can only suggest to have your brother continue to persue this by ticket. A mod might be able to check into it in the morning, but would not know who you refer to, and probably could not share a great amount of details. If you can name a character on either account, or even bnet tags (do not post names or email addresses), it might help.
But in the long run your brother will need to continue tickets.