Multi-model Animations for game

Hey guys and gals,

I’m working on a game right now, and am very interested in learning the “proper” way to create animations using two subjects. Games such as Mark of Kri, any THQ wrestling game, and Chronicles of Riddick for XBox all support animations where the second model appears to run in sync with the main, controlling model. Would this be done as two separate animations, or as one animation with two skeletons? Any insight would be greatly appreciated.

Thanks for the time!