I think some of it depends on what relation you are to the older person.
There are some things I can talk my mother into that others can't because I'm her daughter, and there are some things anyone but me could talk her into because, again, I'm her daughter.
When I lived with my grandmother, I could tell which of her children was calling by the tone of voice she used. My mother was the only one she spoke to with her normal voice. With some of the others, she and them were trapped in dysfunctional patterns that neither of them enjoyed. Both sides would complain about it to me at times, but neither of them would change it.