long story short: Mother died when i was 11, my father started receiving monthly survivor benefits for both of us.

my sister is now living with my grandparents and im worried they’re lying to her. they are shady people and have been pressuring her to sign guardianship papers with the promise that once she signs and they are appointed guardian, that they will open a savings account for her and the survivor benefits would go there directly every month and that it would be released to her in full at age 18.

here are my 2 main concerns

1. the grandparents are wealthy people, so i dont see how they would qualify for receiving that money once they are guardians, since its not like they need it anyway.

2. why would they receive it if it was SURVIVOR benefits for my father. they didnt survive anything, and are perfectly financially capable of taking care of her without any survivor benefits.

any feedback would be appreciated, im basically just trying to figure out if they are lying or not. is what they promised to my sister even possible?

(California, USA)