5 USC 8110 - Augmented compensation for dependents
(a) For the purpose of this section, dependent means
(1) a wife, if
(A) she is member of the same household as the employee;
(B) she is receiving regular contributions from the employee for her support; or
(C) the employee has been ordered by a court to contribute to her support;
(2) a husband, if
(A) he is a member of the same household as the employee; or
(B) he is receiving regular contributions from the employee for his support; or
(C) the employee has been ordered by a court to contribute to his support;
(3) an unmarried child, while living with the employee or receiving regular contributions from the employee toward his support, and who is
(A) under 18 years of age; or
(B) over 18 years of age and incapable of self-support because of physical or mental disability; and
(4) a parent, while wholly dependent on and supported by the employee.
Notwithstanding paragraph (3) of this subsection, compensation payable for a child that would otherwise end because the child has reached 18 years of age shall continue if he is a student as defined by section 8101 of this title at the time he reaches 18 years of age for so long as he continues to be such a student or until he marries.