Rotating Multiplayer Connection Issue

My brother, my nephews and I are experiencing an odd revolving multiplayer connection issue that has us stumped. He has 2 computers on his household network, with one copy of ME3 on each. I live in a separate household with one copy of ME3. He playes on one of his computers and his boys play on the other one. Generally when we have been playing ME3 Multiplayer, I have hosted since my computer is faster and I have the fastest internet connection.

Starting Thursday my nephews were able to connect to me on their computer, but my brother could not on his. We reversed it and he hosted and my nephews could connect to his server, but I could not. We then tried it with my nephews hosting and both I and my brother could connect just fine. We played that way the last 2 days, then today we tried again and I could not connect to my nephews computer but my brother could. We switched it to me hosting and my newphews could connect to my computer, but my brother could not from his. We then tried it with my brother hosting and both I and my nephews were able to connect just fine.

I am seriously scratching my head on this one, as it is rotating around which computer can host all 3 of us for multiplayer. It doesn't make any sense from a networking stand point. We've tried disabling our firewalls, and that made no difference. We've also rebooted everything on both ends, computer, router, modem etc. Nothing seems to make a difference and it keeps jumping around as to which of us can host and still have the others able to join. I'm seriously confused since this issue just started, none of us have done any system or firmware updates, and the only thing that has been patched is Origin.

Is anyone else having this problem, or does anyone have any clue as to what may be causing this rotating connection issue?