Royal Navy officers were not uniformly aristocratic

If most Royal Navy officers were upper class, is a nanny a better comparison for the captain's steward?

The premise is overstated: many officers were middle or upper-middle class, and senior admirals often received their titles for naval service.

Many Royal Navy officers came from firmly middle-class or upper-middle-class backgrounds. British social distinctions therefore matter when describing the officer corps as upper class. Senior admirals often held titles acquired through naval service. Reading those later titles back into their childhoods can give a misleading impression of aristocratic origins.