By keeping them away from their grandparents as much as you can - and by providing a counter example, by serving as role models of non-narcissistic conduct.
To simplify this it's when a person totally controls the wife and children and has no rhyme or reason for any decisions they may make. Here are some clues to emotional abuse regarding wives and...
probably because they don't feel good about themselves so they take it out on their kids and ruin their kids lives like their's were for whatever reason.