Je l'aimais (2009) on Netflix

Plot summary

Adrien, Pierre's son, has walked out on his wife Chloé and on their two small daughters. Chloé had no warning of it, and being left this way leaves her devastated. Her father-in-law Pierre takes her and the two girls to the family chalet, judging that a quiet place and a few days away will help her steady herself. There, over one night, he decides to tell her about Mathilde, the woman he loved, and the easier path in life he followed when he left her. It is a painful secret he has carried and has never spoken of to her.