The royal announced the birth of the couple’s son on Instagram, where she shared a black-and-white photo of herself and her husband holding the infant’s hand.
She captioned the photo with three blue hearts, as well as two exclamation points.
Buckingham Palace also announced the baby's birth in a statement, which read: "Her Royal Highness Princess Eugenie was safely delivered of a son today, 9th February 2021, at 0855hrs at The Portland Hospital.
"Jack Brooksbank was present. The baby weighs 8lbs 1oz."
In the statement, the palace said that the Queen, The Duke of Edinburgh, The Duke of York, Sarah, Duchess of York, and Mr and Mrs George Brooksbank have all been informed and are "delighted with the news".
"This is Princess Eugenie and Jack Brooksbank's first child, The Duke of York and Sarah, Duchess of York's first grandchild, and the ninth great-grandchild for The Queen and The Duke of Edinburgh. Her Royal Highness and her child are both doing well," the statement continued.
The couple, who married in October 2018 at St George's Chapel at Windsor Castle, announced they were expecting their first child on 25 September with an Instagram post.
Sharing a photo of the couple's hands holding a pair of infant-sized slippers, Princess Eugenie wrote: "Jack and I are so excited for early 2021...."
The birth of the couple's first child comes just weeks after the Queen's granddaughter reflected on the three-year anniversary of her and Brooksbank's engagement announcement, captioning a photo of themselves: "This time three years ago... flashback to such a happy moment when Jack and I announced our engagement..."
With the birth, the line of succession changes slightly, with Princess Eugenie's son falling in 11th place in the line to the throne, one place behind his mother.
As a result, the Queen’s third eldest child, Prince Edward, will be shifted from 11th to 12th place.
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