Claim that you and your brother created the account together but that you want one just for yourself now, and that your brother might create one just for him in a little while.

It will prob be ok. It worked for a friend of mine anyway.

Otherwise, if u run XP, just create a new account in XP and then create a new accoutn at Party from that. If u used a credit card the last time, use neteller this time. It will prob not be a problem. And if they notice they will most likely just ask you wich one of the accounts u would like to keep.
However, I wouldn't risk it with a "first time user bonus" since THAT might be considered as fraud if they noticed.

GL

/dNus