The way you get in trouble is that some dork reports you for multiboxing and a GM does a routine check to make sure you are legit. If he sees the accounts are different you are screwed. You might be able to tell a lie and say I am Benjamin James Johnson! 3 of my accounts are under my given name and 2 under what I go by, which happens to be my middle name. I have had a long talk with Billing and they say I won't have a problem because I can prove this.

All that said, the first name seems to make less of a difference if you are transferring toons between accounts.

All of this said keep this in mind 1) this has been my experience and could be totally wrong and 2) using your brother's account goes against the TOS :/