His Social Security does not "count" but if the pension is more than $4700 for the year, you cannot claim him as a dependent. And whether the pension is taxable or not is not relevant.
IRS interview to help determine who can be claimed:
https://www.irs.gov/help/ita/who-can-i-claim-as-a-dependent
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**
