Me and a pal are trying to play some Dawn of War 1 (yes, not DoW II) but we've got some serious connection issues. Basically, we can log onto the online lobbies just fine but we cant connect to each other's games. We've tried everything from opening literally every possible port required, to turning UPnP mode on in our router configuration (since apparently two NAT routers reject each other in DoW but that seems a ridiculous construction to me). Then we've shut off windows firewall, which doesn't help either. What's the matter here?

The strangest thing is that his younger brother can connect to my games fine from his computer, which which is located in the same household, but I can't connect to games -he- hosts, nor to games my mate hosts. My mate can connect to games his younger brother hosts aswell (which seems obvious to me due to them being on a LAN), but he can't connect to games I host.

What's going on here?