Whether a record is helpful depends upon what is known about the family. This World War II draft card (taken from Ancestry.com’s “U.S. WWII Draft Cards Young Men, 1940-1947”), but available from the National Archives, provides evidence of the father’s name and residence as of the time of the registration. It also provides evidence that the father was alive at the time of the registration. In some cases that could be a really big clue.