It would be impossible for blizzard to know the difference from your brother or your dad when it comes to you taking over your brothers account. There is fine lines that will allow this and wont. For instance you live in the same house share the same IP. Blizzard DOES NOT look at how the account is getting paid for or by who is paying for it. As long as it is getting paid. So you have nothing to worry about. I have 4 accounts 5 if you include hubbys. 2 of my accounts are under my maiden name 2 accounts under my married name. I don't pay for 3 of those accounts. My mother-in-law does. So the names are all different from the credit card payment. This as been done for 4 years now. And there has not been a problem. There will only be a problem if I was hacked and I had to prove all the accounts are mine. Which would be a pita.

Now I will back this with what blizzard has said. A friends account was hacked. The hacker revived the account with his/her own game time. When this happened I notified my friend who of course contacted blizzard right away. Blizzards response was. Since this guy/gal is now paying for the account there was nothing they can or will do. The only way for him to get his account back was if he purchased his own time and sent in proof that the account was his. Otherwise the account now belonged to the hacker. All because this hacker was paying for the account as if it was his/hers. My friend finally got his account back after 2 weeks of fighting with blizzard AGAIN. In those 2 weeks the new account owner managed to delete,farm, and cause problems on my friends account.

Blizzard did not care who's name was on the account. They only cared about how it was getting pay for. My friend should of not had to fight with blizzard to get back an account that he purchased the day wow was released. But he did all because this guy PAID to play.

So in closing you pay for it blizzard auto assume's its your account and will do NOTHING unless the orginal owner wants it back.