ah, well if he's not in the same house/network, then you'll need to find out your computers IP, an easy way to do this is to goto
http://whatismyip.com/
then you will give your brother your ip and when he starts Jedi Academy, he can either add your server as a new favorite using the IP and then it will show up in his favorites in Jedi Academy, or he can simply open the console ( shift + ~ [the key to the left of 1]) and type /connect ipaddresshere
for instance, my ip is 209.159.238.23 so someone would type /connect 209.159.238.23
if he can't connect to your server when it's running, then you know you have a port problem and we can go from there.