20 CFR § 404.727 - Evidence of a deemed valid marriage.
(a) General. A deemed valid marriage is a ceremonial marriage we consider valid even though the correct procedures set by State law were not strictly followed or a former marriage had not yet ended. We will ask for the evidence described in this section.
(b) Preferred evidence. Preferred evidence of a deemed valid marriage is -
(2) If the insured person is alive, his or her signed statement that the other party to the marriage went through the ceremony in good faith and his or her reasons for believing the marriage was valid or believing the other party thought it was valid;
(3) The other party's signed statement that he or she went through the marriage ceremony in good faith and his or her reasons for believing it was valid;
(4) If needed to remove a reasonable doubt, the signed statements of others who might have information about what the other party knew about any previous marriage or other facts showing whether he or she went through the marriage in good faith; and
(c) Other evidence of a deemed valid marriage. If you cannot obtain preferred evidence of a deemed valid marriage, we will ask you to explain why and to give us other convincing evidence of the marriage.