Do just what Keeper said. You and the bear could have met when you were young and he was just born. His mom got killed by hunters and you raised him. Whatever you want as a back story feel free to add it to your own as you do need one for your character.
As a matter of fact Ody, Ulthok needs a background to go along with his appearance. 
Chessic, Ayrn how are you guys coming along on your characters? Need any help?