Verified answer

Well as far as offline co-op they stated that would be included in the game at launch. As far as online co-op, lionhead said they would try to get it out with in a week or two of launch, but don't get your hopes up. Hope that helps.

You can join another players game, or they can join yours. But beware of who you invite to your game because they can royally mess up your characters reputation, or kill your "family", and other things that would not make you happy. I don't think 2 people on the same console will work. I do know they will NOT have split screen, so I don't see how it could be possible.

silent hil's got the answer, but you should definatly get it