Porthos, traditionally depicted as a white French noble in Dumas' novels, is recast as the mixed-race son of a freed African slave played by Black British actor Howard Charles, with his backstory explicitly tied to slavery and explored through dedicated plot integration. Aramis is played by Chilean-British actor Santiago Cabrera, altering the character's ethnicity from the source material.

These alterations to pre-existing characters embed identity elements directly into the historical premise rather than treating diversity as incidental. Creator Adrian Hodges framed the series as a 'modern show' that incorporates contemporary issues such as slavery, with the actor citing homage to Dumas' own Haitian-descended father as justification for the changes. This intent shifts focus from swashbuckling adventure to social messaging. Audience criticism at launch highlighted the tension between historical accuracy and perceived political correctness, resulting in reception signals that questioned the necessity of these updates to classic characters.