Exploits of a Young Don Juan (1986)
Original title: Les Exploits d'un jeune Don Juan
Exploits of a Young Don Juan is a 1986 French-language comedy movie directed by Gianfranco Mingozzi, with a running time of 1h 40m. It stars Serena Grandi, Claudine Auger and Marina Vlady.
In 1914, sixteen year old Roger returned home from boarding school during vacation to find his puberty hit hard in a house filled with beautiful women. These women have previous engagements with other men who are away, and during this time, Roger impregnates them all, including his aunt and sister, then devises plans to cuckold the men.
Official site
https://yts.monster/movies/exploits-of-a-young-don-juan-1986