The Geni Consistency Checker will report "Child older than parent" on any profile whose birth date precedes their parent's birth date. Although this is possible for non-biological parents (adoptive, foster, etc.) it would be unusual enough that non-biological relationships are included in this check as well.
This inconsistency is always considered an Error
Auto-fix: There is no auto-fix for this inconsistency. It's possible the child's birth date is incorrect, or the parent's birth date is incorrect, or perhaps this child has been assigned the wrong set of parents.