An employee's wife or husband is an individual who—
(a)
Is married to the employee; and
(b)
Has been married to the employee for at least one year immediately before the date the spouse applied for annuity;
(c)
Is the natural parent of the employee's child;
(d)
Was entitled to an annuity as a widow(er), a parent, or a disabled child under this part in the month before he or she married the employee; or
(e)
Could have been entitled to a benefit listed in paragraph (d) of this section, if the spouse had applied and been old enough in the month before he or she married the employee.