how are billy and his pa and grandpa alike and different?

All three characters appreciate the outdoors. They like the simple life and all have a sort of honour built into their character. There is also a sense of independence, not relying on others to do things for them. This is a common theme in American nostalgic fiction. The differences are in age. Billy is a boy learning about life. Grandfather has a sense of temper that Billy's father does not seem to have.