The median net worth of households in which the head of household is 65 or older is a little more than $250,000. That means half of households in that age group have more money, and half have less.
https://www.nerdwallet.com/article/finance/average-net-worth-by-age
I don't know what your aunt and uncle have, obviously, but perhaps this data will persuade them that there are many seniors who are doing worse in terms of finances.