20 CFR 222.30: When determinations of relationship as child are made.

(a) Determinations will be made regarding a person's relationship as the child of the employee and that person's dependency on the employee (see subpart F of this part) when—

(1) The wife or husband of an employee applies for a spouse's annuity based on having the employee's child in care; or

(2) The employee's annuity can be increased under the social security overall minimum provision based on the child; or

(3) The employee dies and the claimant applies for a child's annuity.

(b) A determination will be made regarding a claimant's relationship as the child of the employee when the claimant applies for a share of a lump-sum payment as a child.