How to Claim. Even though you claim your child as a dependent relative rather than a dependent child, it still appears in the same place on your income tax return. To claim dependents, you have to file using either Form 1040 or Form 1040A. On line 6c, report your adult child's first and last name, Social Security number and relationship to you. Add that dependent to the other exemptions you claim and report the total number of exemptions on line 6d.