I discussed royal titles with Chloe Foussianes at Town and Country Magazine. As the daughter of the Duke and Duchess of Sussex, Harry and Meghan’s second child may be styled as Lady [First Name] Mountbatten-Windsor but as Archie does not use his father’s subsidiary title, The Earl of Dumbarton, it seems unlikely that his younger sister will use a title and will simply be known as Miss [First Name] Mountbatten-Windsor.