Baby Archie and Lilibet will be bestowed with royal titles when their grandfather Prince Charles becomes the King of England.
At the time, Meghan Markle and Prince Harry's children do not have any royal titles, primarily because their parents stepped down from their royal duties in 2020.
The rule that Archie and Lilibet will inherit Prince and Princess titles as the offspring of a son of a King was established by King George VI.
"…the grandchildren of the sons of any such sovereign in the direct male line (save only the eldest living son of the eldest son of the Prince of Wales) shall have and enjoy in all occasions the style and title enjoyed by the children of dukes of these our realms," the 1917 rule dictates.
As revealed by Joe Little, managing editor of Majesty magazine, "As the grandchildren of the Sovereign, they have the right to be upgraded to the style of His or Her Royal Highness. But that begs a question of whether Harry and Meghan want that."
Little continued: "Do they prefer what [Prince] Edward and Sophie have, and not have their children as Their Royal Highnesses with a view to them leading relatively normal lives?"