People don't respond to being told to do things, even by family. It just makes them defensive and even more resistent to changing/improving.

Have you ever read the book "Nudge" by Richard Thaler (who won the Nobel prize for behavioural economics)? He describes a bunch of techniques that move people subtly towards change without being confrontational, and as a result they *choose* to change.

The British govt set up a nudge department, and actually increased the amount of tax paid on time by simply changing the wording on the tax demand. They just added a line saying "the great majority of people in [area where taxpayer lives] pay their taxes on time". And people want to be like the people in their area, so they paid up!

I think families could do with using similar techniques rather than shouting matches, or treating the difficult person as though they were a naughty child.