38 U.S.C. § 1304

No dependency and indemnity compensation shall be paid to the surviving spouse of a veteran dying after December 31, 1956 , unless such surviving spouse was married to such veteran— (1) before the expiration of fifteen years after the termination of the period of service in which the injury or disease causing the death of the veteran was incurred or aggravated; or (2) for one year or more; or (3) for any period of time if a child was born of the marriage, or was born to them before the marriage.