Well, if their the mns of his brothers, would they really get confused? I think they are useable. But if you have a dislike of these brothers and they would think he named them for them, then maybe I would reconsider. But even then,
Joseph and
David have broad histories and probably no one would assume you named them for said brothers. Sorry for the ramble there, hope it made sense :)
Katarina is lovely, it's bit frilly but not pretentious IMO. I would use
Kat as a nn, but I think
Rina or
Kate would be fine.
I've known people with very heavy religious names, and although
Abraham is not my cup of tea, I would be able to take one seriously.