Father Rathe, Defiled Patriarch, is a Unique Hungry Corpse found in the Decaying Crypt Level 2 in Act I of Diablo III. He only spawns for The Family of Rathe event, which always happens in this dungeon.
In combat, he has the Knockback affix. Mother Rathe (his wife) and Little Jebby Rathe (his son) attack together with him, with a small delay. Willa Rathe is his daughter.
Killing him and others will complete the event and put the family to rest.