It was revealed that they have named their daughter Lilibet “Lili” Diana Mountbatten-Windsor.
The royal family responded to the news with their congratulations, with the official royal family Twitter account writing: “Congratulations to The Duke and Duchess of Sussex on the birth of Lilibet Diana! The Queen, The Prince of Wales and The Duchess of Cornwall and The Duke and Duchess of Cambridge are delighted with the news.
“Lilibet is Her Majesty’s 11th great-grandchild.”
The Duke and Duchess of Cambridge Twitter account also Tweeted: “We are all delighted by the happy news of the arrival of Baby Lili.
“Congratulations to Harry, Meghan and Archie.”
What does the name mean - and is it inspired by the Queen?
An official statement from the couple said: “Lili is named after her great-grandmother, Her Majesty The Queen, whose family nickname is Lilibet.”
As a toddler, Queen Elizbeth was unable to pronounce her own name correctly, calling herself “Lilibet” - her grandfather, King George V, began to call her by the nickname and it stuck.
The couple said that their daughter would be known as Lili for short, a variation on the spelling of the name Lily. While each variety of the lily flower has its own meaning, the most common meaning is that of purity, fertility, fresh life and rebirth.
The couple also stated that Lilibet’s “middle name, Diana, was chosen to honor her beloved late grandmother, The Princess of Wales”.
Princess Diana of Wales, Harry and William’s mother, died in a car crash on 31 August 1997.
Is Lilibet in line for the throne?
Despite Harry and Meghan both quitting as senior working royals, baby Lilibet still has a place in the line of succession.
She is eight in line to the throne, after her older brother Archie, who is seventh, and before the Duke of York, who has now dropped to ninth.
Similarly to Archie, who was not entitled to be a prince or an HRH when he was born in 2018, Lilibet is not permitted to be a princess of an HRH due to rules set down more than 100 years ago by George V.
Robert Jobson, an award-winning royal author, explained: "According to a 1917 Letters of Patent issued by King George V, the title of HRH Prince or Princess is passed to ‘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 this realm.
“Both Harry and Meghan know this. Archie, on the other hand, did not qualify to become a prince automatically. In 2012, Queen Elizabeth II issued a Letters Patent to expand on a previous decree that granted such a title only to the eldest son of the eldest son of the Prince of Wales."
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How many great-grandchildren does the Queen have?
The arrival of the second child for the Duke and Duchess of Sussex marked the Queen’s 11th great-grandchild.
Savannah Phillips, daughter of Peter Phillips and his wife Autumn, is the Queen’s eldest great-grandchild at 10 years old.
Isla Phillips is Savannah’s younger sister, who is eight years old.
Prince George is likely the most well known of the Queen’s great-grandchildren. He is the son of Prince William and Kate Middleton and is their eldest at seven years old.
The Duke and Duchess of Cambridge also have two other children - Princess Charlotte, five years old, and Prince Louis, two years old.
Mia Grace Tindall, seven, is the daughter of Zara and Mike Tindall. The couple have two other children - Lena Elizabeth and Lucas Philip.
August Philip Hawke Brooksbank, who is three months old, is the son of Princess Eugenie and her husband Jack Brooksbank .
Archie Harrison Moutbatten-Windsor, two years old, was Harry and Meghan’s first child and then finally Lilibet, the Queen’s 11th great-grandchild.