20 CFR 404.341 - When mother's and father's benefits begin and end.
(2) There is no longer a child of the insured who is under age 16 or disabled and entitled to a child's benefit on the insured's earnings record. (See paragraph (c) of this section if you were entitled to mother's or father's benefits for August 1981.) (If you no longer have in your care a child who is under age 16 or disabled and entitled to child's benefits on the insured's earnings record, your benefits may be subject to deductions as provided in § 404.421.)
(3) You remarry. Your benefits will not end, however, if you marry someone entitled to old-age, disability, wife's, husband's, widow's, widower's, father's, mother's, parent's or disabled child's benefits.
(4) You die.
(c) If you were entitled to spouse's benefits on the basis of having a child in care, or to mother's or father's benefits for August 1981, your entitlement will continue until September 1983, until the child reaches 18 (unless disabled) or is otherwise no longer entitled to child's benefits, or until one of the events described in paragraph (b) (1), (3), or (4) of this section occurs, whichever is earliest.