Under The Piano (1996)

An autistic child growing up in the 1940's and 50's with a mother who is bitter because her fear of success has denied to herself a possible career in opera. This anger translates into an over-protectiveness of her mentally ill daughter, even into the child's adulthood. But a loving sister, herself having an arm that is paralyzed, is a bastion against the limitations imposed by the mother and finally helps her sister to live a more full life.

Unfortunately the movie Under The Piano is not yet available on HBO Max.