Your second scenario sounds like Paulie and Adrian.
I’ve known them some 20 years, since I was a child. He was always saying his half-sister had “the mind of a child.” I’m convinced he wants her to have the mind of a child. For pete’s sake, she can read, write and do math better than most of the public high school seniors in the county, according to the proficiency scores. She can drive a car, and babysit kids and care for his pets; only too dumb to go out on a date?
In a way it reminds me of “Barretts of Wimpole Street.” Elizabeth’s father telling her she was an invalid.