Since Then: Hurley tried unsuccessfully to shelter Walt from the reality of their situation, spelling words to hide their meaning from the child. The two played backgammon together, and Walt consistently won until Hurley owed him thousands of dollars. Once each escaped the Island, Walt came to visit Hurley at the Santa Rosa Mental Health Institute. Years later, Walt ended up as an inmate himself, and Hurley visited him, recruiting him for a job on the Island.
Origin: Walt saw Locke playing backgammon by himself. Locke told him about how the island had healed him.
Since Then: Walt spent a lot of time with Locke in the jungle. Locke taught Walt to throw knives and later helped Michael save him from a Polar bear. After Walt escaped the island, a vision of him discouraged Locke from killing himself. Locke later left the island and visited Walt, who'd been dreaming about him.
Origin: Michael is Walt's father. Michael and Walt's mother separated, and they didn't meet until shortly before Oceanic Flight 815.
Since Then: The two bonded on the Island. They left the Island on a raft, and when the Others kidnapped Walt, Michael pursued them to get him back. He managed to leave the Island with Walt, but only by betraying his friends and killing two people. When he explained his actions to Walt off-Island, his son wouldn't forgive him. Walt moved in with Michael's mother, and Michael died before the two met again. Years later, Walt returned to the Island to help his father move on.