Married widowed assets will

My father married a woman who has kids from another marriage she owned a home in her name only upon her death she put the home in my dads name only but she made a will saying if the house is sold half the money goes to her kids? Is that what will happen even though the home is in my dads name does he have to do that? And if he dies leaving a will saying the house goes to his children from a previous marriage will that happen? Her children are not nice and we’re never there to help their mother when she was sick my dad took very good care of her he takes good care of the house but should he sell it or continue to live in it till he no longer can? Who will have legal rights to the home upon my fathers death or if chooses to sell it to move into elder living facility