Mozzy (DayZ)

Hi Guys, Basic story goes, i recently upgraded my PC and now using old gaming PC for Family use. New PC has Arma installed through Steam and so does old PC. So both PC's have the same 'copy' of Arma on them. Both PC's have DayZ Commander. To my surprise i could play Dayz on both PC's at the same time. Im guessing due to it being a mod it doesnt run through steam so it doesnt give me any 'you've already signed on through a different computer...' issues. So, I can play one server on Dayz and the other PC can play another server, no worries. Ideally i would like to be playing on the same server as the other PC so my brother and i can play together, but we cannot join the others server. The person trying to join the server second gets kicked before the load screen. The obvious solution to this is to set up a different steam account and buy arma 2 all over again but im not keen on paying another £17 for a game my brother probably wont play very often. Im trying to get him into it but he wont play it on his own. Do you guys have any idea how we can get round this? Thanks in advance.

@SP45M Quality response. Insightful. Helpful. Constructive. Beautiful. Well done. @Fraggle Thanks. Thought as much. Just seemed odd that you could play on seperate servers to begin with, therefore wondered if there was in fact a way round the issue? Appreciate it.