5 C.F.R. § 843.211
Someone entitled to an annuity for purposes of §§ 843.203 and 843.204 includes a child, even if the amount of the child's annuity is zero because the amount of the social security child survivor benefits exceeds the child survivor benefits payable under CSRS, unless—
(b) The child is—
[52 FR 23014, June 17, 1987]