According to an in-depth article on the actor by noted film researcher and reviewer Laura Wagner in the Fall 2008 issue of "Films of the Golden Age", and contrary to other references, Warren was not related to actors Henry Hull or Josephine Hull either by blood or via marriage.
At the beginning of his Warner Bros. contract, he was tested for the lead male role in 'Magnificent Obsession' but lost out to another newcomer, Robert Taylor.
He had a daughter, Ann Southwick Hull, by his marriage to Agnes Briggs; he had 3 sons during his marriage to Dorothy Daye.
He was awarded 2 Stars on the Hollywood Walk of Fame for Radio at 6270 Hollywood Boulevard and for Television at 6135 Hollywood Boulevard in Hollywood, California.