20 C.F.R. § 219.51
The following evidence may be required:
(d) If the employee and spouse, widow, or widower were not living in the same household, the Board may ask for evidence that the employee was contributing to or under court order to contribute to the support of his or her spouse, widow, or widower. Evidence of contributions or a certified copy of the order for support may be requested. The court order for support must be in effect on the day the spouse applies for a spouse's annuity or, if the employee is dead, the day of the employee's death. This type of evidence does not apply for purposes of establishing a deemed valid marriage. (See part 222 of this chapter.) A deemed spouse, widow, or widower must furnish evidence as described in paragraphs (a) and (b) of this section.
(Approved by the Office of Management and Budget under control number 3220-0030)