Who is Tengo's Father from 1Q84 and what is their importance?

The man Tengo considers his father is actually his step-father. In his old age, Tengo's father was committed to a sanatorium where he later died. Before dying, however, he informed Tengo that deaths make holes that have to be filled. Over time, Tengo comes to respect and admire his step-father, who so willingly cared for him when he didn't have to.