Les Exploits d'un jeune Don Juan

In the summer of 1914, 16-year-old Roger returned to the family home. The father, a manufacturer of military supplies, the mother, who runs the house, Elisa, 20 years old, the sister engaged to Roland, an aviator officer. There is also Kate, the English governess, Ursule the chambermaid, Hélène, the friendly cook and Madame Muller, the housekeeper. And then there is Berthe, the young sister, 10 years old, of innocent perversity. Suddenly war breaks out and makes all the men leave. Roger finds himself alone. With the vitality of his youth, he dares and realizes all the boldness of his dreams and greedily seduces these women and young girls who discover that they are all fulfilled and delighted. The warriors return, Roger and his partners organize themselves so that the babies that will be born will all have fathers, of which he will be the godfather. It's the least we can do...
(https://www.unifrance.org/film/6312/les-exploits-d-un-jeune-don-juan)