Is he receiving ssi/dis from your social security? The best people to ask would be the IRS customer service department.
1-800-829-1040 listen very carefully to the prompts. You want the option that you want to speak to someone about 'your personal income tax account'. You'll get other options after that, but just stay on the same road of 'Your Personal Income Tax account'
Do Not click on tax information, that will take you to place to order forms and they will repeat the same thing to you. You, make also want to contact a tax attorney and a social security attorney also. But, I would start with the IRS, go online to see if there is an office near you that you could go to. But, of the field offices are closed after tax time.