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.