No, since you are not paying for at least half their support. I have asked my tax accountant this question in the past beccause my MIL is on Medicaid in a LTC facility.
In order to claim them as a dependent, you have to provide over half of their care. It sounds like Medicaid and SSI is providing their support and not you, therefore, you cannot claim them on your taxes.
If they are in a nursing home, you are non financially supporting them. Perhaps you pay for a few things they want/need here and there, but it would be very doubtful you pay for more than 50% of their expenses.
Their SS income does not go to Medicaid. It goes to the nursing home with Medicaid paying the balance of what their SS doesn't cover. At this point, the SS plus the Medicaid (state funds) is paying for their food, shelter, and medical expenses - those programs support your parents.
Twila1: No, being their principal (POA) does not mean that you can claim them on your tax filing status. In addition, none of your funds are going towards their care that would enable you to claim them.
Their SS income does not go to Medicaid. It goes to the nursing home with Medicaid paying the balance of what their SS doesn't cover. At this point, the SS plus the Medicaid (state funds) is paying for their food, shelter, and medical expenses - those programs support your parents.