In the United States, most of the Italian produced sword and sandal/mythological muscle man movies were booked by exhibitors into their "B" theaters, usually as part of a double feature. With the teaming of both Steve Reeves and Gordon Scott, Paramount was able to get this booked into many "A" theaters as a single feature.
The producers originally wanted Steve Reeves to play both Romulus and Remus, but he declined to do double roles and recommended former Tarzan Gordon Scott.
For its U.S. release, Paramount changed the title to the more dynamic sounding "Duel of the Titans." There was also the concern that most Americans would not know who Romulus and Remus were.
To insure that the American public knew who the two stars were, the promotional material released by Paramount listed them as "Steve (Hercules) Reeves" and "Gordon (Tarzan) Scott."
Steve Reeves and Gordon Scott, playing twin brothers Romulus and Remus, may not have shared a birthday, but they were both born in the same year - 1926.