I would liken the relationship between the old man and the boy to something similar to a father and son relationship. Readers get see this relationship in action in the early parts of the book. The boy and the old man are not related; however, the narrator makes it clear that they have spent years interacting with each other. Their conversation is easy and ranges from fishing to American baseball. The old man taught the boy to fish, and the boy is forever grateful for the old man having taught him that. This is probably why the boy is with the old man in the beginning of the story. He is worried about the old man's health and the fact that he hasn't caught any fish in a long time. It's a small role reversal from the old man taking care of the boy and teaching him to fish. This time, the boy tries to help the old man. For example, the boy buys him some sardines. Readers also get a really great image of the boy becoming the man's caretaker when the old man falls asleep and the boy covers him with a blanket.