the movie where the young boy and girl watching a adult women breastfeeding her child

The movie you are referring to might be "Blue Is the Warmest Color" (original title: "La Vie d'Adèle") directed by Abdellatif Kechiche. In this film, there is a scene featuring a young boy and girl who watch a woman breastfeeding. The film explores themes of love, sexuality, and the complexities of relationships. If this is not the film you meant, please provide additional details, and I'll be happy to help further.