20 CFR 219.42: When evidence of child's dependency is required.

Evidence of a child's dependency on the employee is required when—

(a) The employee is receiving an annuity that can be increased under the social security overall minimum (see part 229 of this chapter) by including a child, grandchild or a spouse who has a child in his or her care;

(b) A wife under age 65 applies for a full spouse annuity because she has a child or a grandchild of the employee in her care; or

(c) A child or someone in behalf of a child applies for a child's annuity based on the deceased employee's record.