Tendres cousines / Cousins in Love (1980)

Summer 1939 in the Provence, France: the 14 years old Julien has a crush on his cousin Julia, who lives together with his family in their small hotel. Unfortunately she ignores him, because she's several years older. Then the hotel guest Charles enters the competition, a slimy twenty-something who lusts for the girl, despite the fact that he's engaged.

Imdb