Master and Commander is a great movie! I never read the Aubrey/Mauratin novels. While I knew of the Hornblower series I read Alexander Kent's Bolitho series. In that series, Bolitho never had a confidant friend like Aubrey does, but he did have loyal subordinates whom he appoints as the captain's coxswain. The first was a black man named Stockdale whom Bolitho, when on a pressgang to get more sailors, convinces him to leave the prizefighter world of boxer. Stockdale dies protecting Bolitho's back from enemy snipers as their ships battled the enemy. He then takes on another coxswain Allday who was a bit of lower deck rebel but devoted to the navy.