If he had less than $4700 of income not counting Social Security you can claim him as qualified relative and get the $500 credit for other dependents. If he had more than $4700 of income you cannot claim him.
CREDIT FOR OTHER DEPENDENTS
You may be able to claim him as dependent under the Qualifying Relative rules as long as his gross income in 2023 was less than $4,700.
To be a Qualifying Relative -
1. The person cannot be your qualifying child or the qualifying child of any other taxpayer. A child is not the qualifying child of any other taxpayer if the child's parent (or any other person for whom the child is defined as a qualifying child) is not required to file an income tax return or files an income tax return only to get a refund on income tax withheld.
2. The person either (a) must be related to you or (b) must live with you all year as a member of your household.
3. The person's gross income for the year must be less than $4,700 (social security does not count) in 2023
4. You must provide more than half of the person's total support for the year.
5. The person must be a U.S. citizen or a U.S., Canada, or Mexico resident for some part of the year.
6. The person must not file a joint return with their spouse.
Probably - if he has less than $4700 in income. Here are the other requirements - See Qualifying Relative