20 CFR §218.42

1. (a)Tier I. The tier I benefit of a parent annuity ends with the earliest of the last day of the month before the month in which the parent—
   1. (1)Dies;
   2. (2)Becomes entitled to an old age benefit under the Social Security Act that is equal to or larger than the tier I benefit of the parent annuity before any reduction for the family maximum, unless he or she is also entitled to a tier II benefit (reduction for the family maximum is discussed in part 228 of this chapter);
   3. (3)Becomes entitled to another survivor annuity in a larger amount, unless he or she elects to be paid the smaller annuity; or
   4. (4)Remarries after the employee's death, unless he or she marries a person who is entitled to Social Security or Railroad Retirement Act benefits as a divorced spouse, widow, widower, mother, father, parent, or disabled child.
2. (b)Tier II. The tier II benefit of a parent annuity ends with the earliest of the last day of the month before the month in which the parent—
   1. (1)Dies;
   2. (2)Remarries after the employee's death; or
   3. (3)Becomes entitled to another survivor annuity in a larger amount, unless he or she elects to be paid the smaller annuity.