You have one router and two Xboxes. If two of you in the house want to play an online game at the same time, the following might sound familiar.
It all starts with NAT or Network Address Translation. This is a technology that allows more than one computer to be on the Internet at the same time using the same IP Address. The type of NAT you use determines how easily your console can talk to another console across the Internet. There are three different NAT types:
To have the very best connection and best online gaming you need to have Open NAT. To do this you need to use port forwarding.
To attain open nat on one Xbox you simply forward port 3074 (UDP and TCP). To get open NAT when you have more than one Xbox on your router you need to use a second port. This is where the problem lies. Xbox has allowed the use of port 3074 (UDP and TCP) only. However if you have another Xbox console you cannot forward that same port to the second console. A port only allows one set of data to pass through at a time. This works great for the primary Xbox but the secondary Xbox will lag and have trouble playing an online game in general. To solve this problem Activision has made it so you can port your second Xbox to 3075 (UDP and TCP). If you have a third console go ahead and port 3076 (UDP and TCP) to that one.
The short answer is possibly. The longer answer is that this trick is confirmed to work for Activision games but why not try it with other games, it may just work. Good luck!