Unable to play Multiplayer with 2 PC's on the same IP

Whenever i'm online, just online, not even in game (DA:I) my brother on a seperate PC in another room which is connected to my router can't play Dragon Age: Inquisition Multiplayer. Whenever he tries to connect to a game he gets "Lost connection to session" and whenever he opens a match and someone tries to join in he gets booted out with the same error. I tried connecting to him and that doesn't work aswell in most cases, in case it works he gets booted out again as soon as i manage to get in.

I tried everything i can think off, all kind of router options, configurations, switching accounts, switching PC's, disabling antivirus software, disabling firewall, the entire collection of stuff and i found out that if he connects through Korean VPN to the game he is able to play with me but of course extremely laggy and in an absolutely unplayable way. It has something to do with us connecting to the servers with the same IP and it definetly seems to be related to Dragon Age Inquisition. Mass Effect 3 MP as example works perfect, connecting to each other works too, i can even browse his entire PC if i want and vise versa.

Please fix this, playing through VPN is absolutely unacceptable. Allow same IP connections.