I saw this movie when I was a child. I am almost certain it was in the eighties or early nineties. This was a TV movie. It was in color. A twin girl was angelic. She lived with nuns at a nunnery. I remember a scene where she heals a dead bird. Her twin brother was evil. It was a good vs. evil type movie. I am thinking the brother wanted to kill his sister. This is about all I can remember.
Could it be Child of Darkness, Child of Light?
https://youtu.be/CHO6IgVp8JM