Stéphane Petitbourgeois is having trouble with his son-in-law Hubert, who has an extra child every year and is expecting his ninth, making thirteen people in the same apartment. However, a competition promises twenty million to the youngest grandfather of twelve grandchildren. Stéphane begins to encourage Hubert. But Pat became sterile from that day on. Finally, after two years, a child is announced. In fact, triplets were born, and after a few twists and turns, Stéphane became the youngest grandfather of twelve grandchildren.
Jane Sourza
as Isabelle Petitbourgeois, la femme
Raymond Souplex
as Stéphane Petitbourgeois, le mari expert-comptable
Louis de Funès
as Célestin Ratier, représentant des industries de l'enfance
Jean Carmet
as Hubert, le beau-fils
Andrée Servilanges
as Geneviève, dite Mademoiselle, la nurse
Andréa Parisy
as Pat, la fille
Marthe Alycia
as Daphné, la mère d'Hubert
Florence Blot
as l'employée de l'état civil
Saint-Granier
as lui-même
