Cousin, Cousine
Two distant cousins meet at a wedding banquet for an elderly couple. Over time, a close friendship develops between them, but their spouses begin to think that they are more than just friends.
Starring Marie-Christine Barrault, Victor Lanoux, Marie-France Pisier, Guy Marchand, Ginette Garcin, Sybil Maas, Popeck, Pierre Plessis, Catherine Verlor, Hubert Gignoux
Watch "Cousin, Cousine" on Criterion Channel released in 1975. It's a comedy and romance movie, and has a rating of 6.8 out of 10 from Imdb which is usually fine for this kind of movie.