how do i have a guardium adlitium to protect my grandchildren now there father has passed and the parents are not married

there father died two weeks ago and his sister has taken all vehicles documents all rights to his estate and money he had a pay on death account to her which he indented to be for there care in the sum of $ 200,000 she is a paralegal and he a alcoholic and a drug user and my concern how do I protect my daughter and grand children. they live in the home where he passed and need to know if they will continue to have a home and be able to pay there bills,she told them to apply for social security and state help but they can stay as long as my daughter is able to pay the bills,how ever she is selling the new vehicles