If Form 1040, Line 1 checkbox "Single" or Line 4 checkbox "Head of household" or Line 5 checkbox "Qualifying widow(er) with dependent child" is checked ('IndividualReturnFilingStatusCd' has a value 1 or 4 or 5),
then each qualifying child on Schedule EIC(Form 1040) must be younger than the tax payer.
Check the date of birth for the 3rd child you listed.
