If There Be Thorns(2015)

Christopher and Cathy Dollanganger live together as man and wife with Cathy's two sons who are unaware of the incestuous nature of their parents' relationship. But when a mysterious woman moves in next door and befriends the younger boy, Bart, he begins a strange transformation and displays accusatory behavior towards Cathy and Christopher. When Christopher discovers their mysterious neighbor is, in fact, his mother Corrine Dollanganger, all of the family's long-hidden secrets are revealed in a tragic climax.