Two English Girls (1971)

At the beginning of the 20th century, Claude Roc, a young middle-class Frenchman meets in Paris Ann Brown, a young Englishwoman. They become friends and Ann invites him to spend holidays at the house where she lives with her mother and her sister Muriel, for whom she intends Claude. During these holidays, Claude, Ann and Muriel become very close and he gradually falls in love with Muriel. But both families lay down a one-year-long separation without any contact before agreeing to the marriage. So Claude goes back to Paris when he has many love affairs before sending Muriel a break-off letter...

Source: TMDb