Split Screen Online Games for 360?

Specifically what I'm talking about are systems like Halo where a couple of people could be playing splitscreen locally, but still able to enter online modes. Reason being my brother and his girlfriend just bought a 360 and want to play the rest of the family together. Extra points for games that don't require Xbox gold for profiles on the same system.

Halo 3

Call of Duty 3

Risk: Factions (requires gold for all people playing online)

What I've discovered so far

Dungeon Defenders is one but requires gold for both (which is dumb) also it's free for gold members till the end of the month.

Also pretty sure Trenched *cough* "Iron Brigade" is a split screen online game. Can't remember if you require gold or not for both.