Callistemon I absolutely agree with all you say, but I have also seen cases, where it is a relative that is doing both, the cutting off and the fleecing of the money.
I was a home visitor with a charity for older people for over 10 years and in that time saw about every combination of relationships of children, older people and outside relationships you can imagine. Including exploitative ones, though never sexual exploitation.
This story is horrendous and shows what can happen at extremes, But I saw, but was unable to intervene, in a case where the exploiter and abuser was a son and what was happening, stopped just short of murder.....