Brother and I are trying to play BF3 together, yet the game disconnects one of us when trying to join the same server. Any ideas on a fix?

I've done a bit of googling, and even found a solution for bad company 2, which had the same problem, and the fix was switching ports for each copy, but it seems you can't change the ports for bf3.

Has anyone here overcome this?

My older bro bought the game to play it with me, and he's feeling like he's out $60 right now.