Or better yet were they notified by mail? Was it in person at the draft office once they were deemed fit to serve? I'm writing a story set in the 1940s and have virtually no concept of how the draft worked.
Another question I have is was it possible for more than one immediate family member to be involuntarily drafted?
When is the exact time in the story in which you are concerned about the draft? The mechanics of the draft differed significantly even from 1940 to 1945. If selected, men were mailed a Notice to Report for Induction (D.S.S. Form 150).
I wrote a post about the draft here.