Chapter 3 argues that the family is not just the beginning of the moral life but the pattern for the Kingdom of Heaven. The home is a textbook whose lessons can be enlarged into nation, world, and cosmos.
Its central movement is outward. A person learns to love grandparents, parents, spouse, siblings, and children in the family so that the same quality of heart can be extended to all humanity. In that sense, the world is an enlarged household.
The chapter also gives the family a temporal depth. Grandparents represent the past, parents the present, and children the future, so a true family gathers history and destiny into one sphere of inherited love.