If the dependent earned no other income than
Social Security during the tax year, the income is not taxable or reportable,
and thus a return is not required.
If the child has enough other income to be
required to file, then he/she should report the Social Security on his/her
return.
If the child lived with his mother over 6 months in 2017, unless you provided over one half the child's support, you cannot claim him as your dependent
See Dependent Calculator
