Not since the birth of Prince George in 2013 has a royal baby been so eagerly anticipated.

But while Prince Harry and Meghan Markle’s baby is set to be the most famous newborn of 2019, their child will have a decidedly less important title than their cousins unless a major family shake-up occurs between now and the birth.

According to the Letters Patent issued by King George V in 1917, only the grandchildren of a monarch or those in direct line to the throne can be styled as a prince or princess.

“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 decree states, according to Good Housekeeping.

Meghan Markle shows off her growing baby bump on Monday, Nov. 19, 2018. (Getty Images)

This means that the great-grandchildren of the monarch do not automatically receive HRH titles except for Prince Charles’s oldest grandson, Prince George.

As a result, the Duke and Duchess of Sussex’s offspring will be known as either Lady or Lord Mountbatten-Windsor unless one of two things occurs before their first child’s birth.

If Queen Elizabeth dies before the baby is born — which is speculated to be in either late March or early April — and Charles becomes king, then Meghan and Harry’s child will be an automatic prince or princess.

Otherwise, the 92-year-old monarch could use her discretionary power to make Harry and Meghan’s child a prince or princess.

Meghan Markle and Prince Harry are reportedly planning to travel to the U.S. after the birth of their baby, royal expert Katie Nicholl says. (Chris Jackson - Pool/Getty Images)

The Queen has stepped in before to give royal titles to all of Kate Middleton and Prince William’s children, as protocol would otherwise mean only George as the male heir would have been a prince.

But it’s possible Harry and Meghan could decide not to have their children styled as princes and princesses at all, with Charles’ younger brother Prince Edward opting out of the titles for his offspring.

Edward and his wife Sophie Rhys-Jones surprised royal watchers by deciding that their children would not be HRHs when they married in 1999.

A palace spokesman at the time said their decision reflected “the clear personal wish of Prince Edward and Miss Rhys-Jones as being appropriate to the likely future circumstances of their children”.

(Reuters)

Instead, the Earl and Countess of Wessex’s two children are known as Lady Louise Windsor and Viscount Severn, who will one day inherit his father’s title.

This article originally appeared on news.com.au.