A Little Piece of Heaven (1991)

Will Loomis is living with his mentally handicapped sister Violet, who wants a younger child to play with, so Will 'kidnaps' one (and then another) child from the local children's home. The child is told it is dead and gone to heaven. Will and Violet try to make their farm a little piece of heaven for the kids, while the authorities wonder what has happened to the kidnapped children.

Unfortunately the movie A Little Piece of Heaven is not yet available on HBO Max.