Because he is on disability and qualifies for no additional help he depends on me to help him get groceries, gas etc...
If he lived with you for the whole year and had less than $5050 of income not counting Social Security, then you might be able to claim him as a "qualified relative" and get the $500 credit for other dependents.
IRS interview to help determine who can be claimed:
https://www.irs.gov/help/ita/who-can-i-claim-as-a-dependent
Qualifying relative
When you add someone as a dependent, we'll ask a series of questions to make sure you can claim them. There may be other tax benefits you can get when you claim a dependent.
Related Information:
In order for you to claim an unrelated adult as a dependent, they would have to live with you the entire year, and must also fit these criteria:
The credit is $500 per qualifying dependent as long as your adjusted gross income (AGI) doesn’t exceed $200,000 ($400,000 if filing jointly). The credit goes down $50 for every $1,000 that the AGI exceeds the $200,000/$400,000 limit.
See this IRS webpage for more information.