The Robinson family consists of a father, a mother, and four sons: Fritz, Jack, Ernest, and Franz. The characterizations of the sons are vague, although they do have some unique qualities. The mother is strong and quiet with virtually no discernible personality.

The pastor-father occupies the chief role. He has an incredible knowledge of nature and identifies every tree, herb, and flower for his sons. He uses the Socratic method to teach his family, helping them find their own answers to their questions.

Often the action of the story is interrupted for one of the father's moralizing digressions. He keeps a journal through the ten years of their confinement on the island, and at the end of the tale he gives the manuscript to his sons who are leaving for Europe. His remarks as he hands over his journal reflect the purpose of the...