#4 - June 29, 2009, 8:03 p.m.
Currently, there is no way to access the same account from two separate computers simultaneously. Additionally, as a few players have pointed out, our Terms of Use prohibits the sharing of accounts except in the situation where a parent or guardian allows one minor child to access the account. With that in mind, it would probably be best to avoid sharing an account with your brother due to the security concerns that may arise.
If you and your brother are considering creating your own individual accounts, you may want to look into the Recruit a Friend system. This promotion offers several benefits to both players involved such as faster leveling, summoning, and many more. Additional information on the Recruit a Friend system and its benefits can be found on the following links:
Recruit-A-Friend FAQ http://us.blizzard.com/support/article.xml?articleId=20588 Recruit-A-Friend Procedure http://us.blizzard.com/support/article.xml?articleId=26269