§ 1901. Definitions
For the purposes of this subchapter—
(2)
The terms “widow” or “widower” mean a person who was the lawful spouse of the insured at the maturity of the insurance.
(3)
The term “child” means a legitimate child, an adopted child, and, if designated as beneficiary by the insured, a stepchild or an illegitimate child.
(4)
The terms “parent”, “father”, and “mother” mean a father, mother, father through adoption, mother through adoption, persons who have stood in loco parentis to a member of the military or naval forces at any time before entry into active service for a period of not less than one year, and a stepparent, if designated as beneficiary by the insured.