Queen’s ruling affects Baby Sussex’s title
Baby Sussex is seventh in line to the throne but will not be named a prince unless special permission is granted by his great-grandmother, Queen Elizabeth.
Royal decrees from a century ago mean Prince Harry and wife Meghan's boy will not automatically carry the title "Royal Highness.''
Instead, their new son would be more likely be known as "Lord'' followed by their first name.
In 1917, when King George V was looking to streamline the monarchy, he decreed that only the eldest son (Prince George) of the eldest son (Prince William) of the eldest son (Prince Charles) should be entitled to be called Prince.
The Queen made a special ruling in 2013 to ensure all of Prince William and Catherine's children became royal highnesses, but the dispensation does not apply to other royal babies, including Prince Harry's offspring.
The Queen had previously offered to make all of her grandchildren from her four children - Prince Charles, Prince Andrew, Princess Anne and Prince Edwards - royal highnesses but only Prince Andrew accepted, making princesses of his daughters Eugenie and Beatrice.
Princess Anne refused any titles for her children, who are known simply as Peter Phillips and Zara Tindall.
Prince Edward accepted courtesy titles of James, Viscount Severn, and Lady Louise for his young son and daughter.
Royals don't take usually use last names, but if Prince Harry follows his brother Prince William's lead, his sons could take the last name of his dukedom, and use the name Sussex.
On the up side, they won't have to ask the Queen's permission to marry once they reach adulthood, as a reform of royal succession laws in 2013 mean only the six royals closest in lineage to the Queen have to seek her approval, as Prince Harry did.
"There's only one magic number and that is that the first six in line require the consent of the
monarch before they can get married," Professor Robert Hazell of University College London's Government and Constitution Unit told News Corp Australia ahead of the baby announcement.
"It's entirely up to the Queen whether she wants to bestow any type of title on the new babe and if so, what.
"It's very unlikely that the child will be called a prince."
Prince Harry and Meghan the Duchess of Sussex's first child will bump Harry's uncle Prince
Andrew, the Duke of York, out of seventh place in the line of succession.
The child's grandfather Prince Charles is the heir apparent and first in line, followed by Prince
William, William's children Prince George, 5, Princess Charlotte, 4 and Prince Louis, a year old, and Prince Harry.
The distance from the throne means the boy will almost certainly never be sovereign, and will not have to adhere as rigidly to royal rules as cousins George, Charlotte and Louis will. They will also drop significantly down the royal rankings once their cousins have children of their own.
Despite this increased freedom, Prof. Hazell said the boy would still live their life in a "gilded cage".
"This poor child is not going to have a normal life, not as you and I understand life to be," he said.
"The public often think they live such lovely privileged lives in palaces with servants, waited on hand and foot.
"If you think about it for a moment, you would not want to exchange your life with theirs."