Well, I can answer the part about why setting the port to 27959 caused it to not show up any more for you and your bro. It was showing up on the local network, which searches LAN computers for servers on the default port. It doesn't search on port 27959.
As for not showing up for anybody else, it's probably a matter of setting the port forwarding on your router to correctly forward to the machine running the server, as others have suggested.