Casey and Fin may be best of friends, but in the animal world, one is going to be dominant over the other. This is not a problem, unless dominance is in contention, and then there's a lot of arguing going on.

If they are sleeping together in the bed, the argument has been settled. It sounds like Casey is the dominant figure in the house. When he gets tired of claiming Finnigan's bed, he'll move on.

The cat cubby may or may not fly. Afterall, you can't herd a cat. Of course, a little cat nip for persuasion purposes may not be a bad idea. Worst case scenario is that Casey will adopt the cat cubby AND Finnigan's bed. That's just the way with cats--gotta love 'em.