Prince Harry and Meghan Markle's little one will not have a royal title to match.
Thanks to the unborn royal's great-great-great-grandfather, King George V, the little royal's name likely will not be styled with an HRH or prince or princess title, according to the Daily Mail, as in 1917, King George V limited titles within the royal family.
"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," King George V's decree reads.
As a great-grandchild of the Queen, the Duke and Duchess of Sussex's child will be too far down the line of succession to be an HRH, and will instead become Earl of Dumbarton, one of the subsidiary titles Prince Harry received from Queen Elizabeth II on his wedding day, should the child be a son. Prince Harry's daughter would be Lady [First Name] Mountbatten-Windsor, and any subsequent sons would be Lord [First Name] Mounbatten-Windsor.
It is possible that the Queen will overrule the decree and allow Prince Harry and Meghan Markle's children to be HRHs and princes and princesses. In that case, Prince Harry's sons will be styled as His Royal Highness Prince (His Name) of Sussex, while daughters will be known as Her Royal Highness Princess (Her Name) of Sussex.
Ahead of Prince George's 2013 birth, Queen Elizabeth II issued a Letters Patent that ensured Prince William's children had fitting titles, meaning that Princess Charlotte and Prince Louis were given HRH titles. Without the Letters Patent, only Prince George, the eldest son of the eldest son of the Prince of Wales, would have been a prince.
Baby Sussex will supersede Prince Andrew in the royal line of succession regardless of sex, due to the Succession of the Crown Act, passed by the U.K. Parliament in 2013, which granted the same status to daughters and sons.
Upon the new royal's birth, the new line of succession will be Prince Charles; Prince William; Prince George; Princess Charlotte; Prince Louis; Prince Harry; Baby Sussex; Prince Andrew; Princess Beatrice; Princess Eugenie; Prince Edward; James, Viscount Severn; Lady Louise Windsor; Princess Anne; Peter Phillips; Savannah Phillips; Isla Phillips; Zara Tindall; Mia Tindall; and Lena Tindall.
Regardless of the little royal's official title and his or her line in the succession to the royal throne, it remains to be seen what the Duke and Duchess will choose to name their little one. Currently, top contenders seem to be Arthur, Phillip, and James for a son, and Diana, Alice, and Victoria.