My step dads doctor told him he has dementia a year ago. A few days later his kids were taking him to sign all kinds of papers and power of attorney to them. Then they took him out of the senior care center and left my mother with no money in their back account and she has not heard from them for 4 months now. She does not know where he is or how he is. She has stage four cancer, has heart problems and is getting a shoulder replacement. She only gets $438.00 a month. What are her legal rights?
You need to take her (if she's able) to a lawyer. There is NO way his family can leave her destitute. You can file charges that they have kidnapped him (if he wasn't mentally able to agree to leave) and have robbed him and her of all their money.
I'd also file a police report of his disappearance and missing money. It would be helpful if you had his children's names that could have been involved.
File for emergency need with the county for welfare (it's called something else now), food stamps, etc. until they can find your step brothers and sisters who are responsible for this terrible act.