Should my brother file taxes - He gets $15,043 in SSD and $5,338.84 in Pension. He is single with no working income

Probably not, since he will not have any taxable income to be reported on the tax return.

Up to 85% of Social Security Retirement/Disability/Survivors benefits becomes taxable when all your other income plus 1/2 your social security reaches:

Married Filing Jointly - $32,000
Single or Head of Household - $25,000
Married Filing Separately - 0

You need to file a federal return if half your Social Security plus your other income is

Single or Head of Household      $25,000

Married Filing Jointly                  $32,000

Married Filing Separately            $0

But if he has a 1095A for marketplace health insurance he is required to file a tax return.