While Culhwch and Olwen, also found in the Mabinogion collection, is primarily an Arthurian tale, in which the hero Culhwch enlists Arthur's aid in winning the hand of Olwen, daughter of Ysbaddaden the Giant, it is full of background detail, much of it mythological in nature.
As in Percival the hero's father dies when he is young, and his mother takes him into the woods and raises him in isolation.