20 CFR § 404.760 - Evidence of living in the same household with insured person.
If you apply for the lump-sum death payment as the insured person's widow or widower, or for wife's, husband's, widow's, or widower's benefits based upon a deemed valid marriage as described in § 404.727, we will ask for evidence you and the insured were living together in the same household when he or she died; or if the insured is alive, when you applied for benefits. We will ask for the following as evidence of this:
(c) If you and the insured person were temporarily living apart, a signed statement explaining where each was living, how long the separation lasted, and why you were separated. If needed to remove any reasonable doubts about this, we may ask for the signed statements of others in a position to know, or for other convincing evidence you and the insured were living together in the same household.