For livetiludye
Here is some settings I found that fixed a father and son having problems seeing each other in lobbies or being able to even get in the same lobbies.
Turn UPnP off on the router. Disable DMZ also. You shouldn't have this on if you are forwarding ports.
I beleive you just need to forward Ports 3478, 3479, and 3658. Forward them just to ONE of the PS3s. That will be the PS3 that will create the lobby. Have the other PS3 join this lobby.
Your port redirection should look like this.
INC - OUT TYPE -> DEST IP
3478-3478 UDP -> 192.168.2.10
3479-3479 UDP -> 192.168.2.10
3658-3658 UDP -> 192.168.2.10