Board Thread:Lore Discussion/@comment-5613590-20130707010500/@comment-11227880-20130708101243

i am assuming he either met a wolf cub during his adventures with Gwyn or defending oolacile

OR

Since he is friends with Alvina of the Forest, he befriended a wolf cub or wolf pack and he became friends with one such wolf, that he named it Sif, and the two became a Duo.