Do children have any legal standings against father?

Recently my father remarried, after losing our mom to cancer 5 years ago. Prior to our moms death she had set of trust fund for all my dads care and living expenses. 3 years ago he met his new wife and asked her to move in. She agreed , but insisted that not only she be put on the title to the house and all his assets. At that time my siblings and I found it odd and not only confronted her but insisted that to our father that he not only resist to make changes until he decided if they were going to share there life together or were just housemates. Ever since this time, she has done everything turn our father against us. when they did get married this summer , she made it known that we were not welcome at the house my parents called home , but changed all assets to her . THe only thing in the house that we really want is our moms ashes; as she has never been straight and honest with us. We fear that when my father passes , she will throw her ashes away. please advise