If you live with your parents then as Perna says, that money is given on your behalf to help defray the costs of your living expenses because you are unable to do so yourself.
I don't know how old you are, or the nature of your disability, but if you're of age, look into low income housing etc. I say look into because most people find it extremely difficult to live on disability, that is pay for rent, food, utilities. Luxuries are unheard of.
If you are already on your own and they are requesting money, the only thing you can do is tell them that you cannot afford help them.