2 players on same network causes crash for other player?

This bullshit has been going on for almost 2 years now, and its to the point where I want to know why. When my brother and I try to join the same server, occasionally, when I join he looses his connection to the server. After that, neither one of us can join the server and get stuck at Parsing Game Info. If I do not try to join, he is able to get in. But the minute I join he loses connection. The same results can be given if it is the other way around. If I am in a server, and he joins, I lose my connection. What is the cause of this so that way I can fix it?

Having the same IP. Try forcefully changing your client port to something obscure using -clientport in the advanced launch options, though I doubt that’ll fix it.

I’m trying that now, Although I don’t think that’s the case. This seems to be an intermittent problem. If it was something as simple as the IP, then it would fail 100% of the time. It only does this about 15% of the time.

EDIT:
Yeah. It didn’t work… Was worth a try though.