This is way late in response, but what the heck :)
Not sure about today, but back in the 60's, if a man lost his father in combat, he was automatically excluded from being drafted. My Grandfather was killed in the Malmedy Massacre (Battle of the Bulge) in December 1944. My father had been born in October 1944 and months later, his father was shot and killed, never getting word that his son was born, just knew that his wife was expecting.
My father was of age during the Vietnam draft, but was not called to action because of his father being KIA. It is likely that my Grandfather's death, saved my Dad's life. The son he never even knew he had.