The authors emphasize the importance of nuclear family in both the human and animal worlds throughout the book. The story is the product of the 1930s—a simpler, less diverse societal period in American history. The Poppers have a very traditional marriage: Mr. Popper is a housepainter who works hard at his trade but does not earn a high income, while Mrs. Popper is a traditional housewife who worries about cleaning, providing good family meals on a seasonally reduced income, and participating in local volunteer activities. Although Mr. Popper has the soul of an artist and an adventurer, he is never embittered by his profession as a housepainter. Rather, he is accepting of the fact that his role in the family requires him to produce income in this way, and he rejoices in the company of his wife and children. Similarly, Mrs. Popper expresses concern about unpaid bills, but she never expresses disappointment about her husband’s capacity as a breadwinner. Both individuals value each other and cherish their children.

This theme is mirrored in the family life of the penguins. Captain Cook languishes until he is provided with a mate, Greta. The pair produce 10 chicks and follow their instinct to procreate the next generation.