Bro's wife mistreats them but they won't leave them...

Dear Diana,

My brother's wife lives with my parents, mistreats them to the extent that they never have known any peace in the last five years. My brother works on a ship and always buys his wife's version of the 'truth'. My husband and I keep asking them to come live with us, but they refuse to, as they love being with their grandchildren [we just got married a year back and have no children yet], and can't bear the thought of being away from them. We live in a different city and they don't want to move.