Princess Eugenie and her husband Jack Brooksbank today announced they are expecting their third child - with the King saying he is 'delighted' with the news.
Buckingham Palace officials also revealed the couple's sons August, five, and Ernest, two, are 'very excited' to welcome a younger sister or brother to the family.
In a photo shared by Eugenie, Ernest, wearing a Chelsea football kit, and August, wearing a long-sleeved grey T-shirt, can be seen holding a picture of a baby scan.
The 36-year-old princess posted in an accompanying caption on Instagram: 'Baby Brooksbank due 2026!' followed by a series of red heart emojis and one of a baby.
A Buckingham Palace statement said: 'Her Royal Highness Princess Eugenie and Mr Jack Brooksbank are very pleased to announce that they are expecting their third child together, due this summer.
'August (aged five) and Ernest (aged two) are also very excited to have another sibling join the family.
'His Majesty The King has been informed and is delighted with the news.'
The baby, who will not be an HRH, will be born 15th in line to the throne, with their great-uncle, the Duke of Edinburgh, moving down to 16th place.
In a photograph shared by Princess Eugenie today, Ernest, wearing a Chelsea football kit, and August, wearing a long-sleeved grey T-shirt, can be seen holding a picture of a baby scan
Eugenie and Jack Brooksbank are spotted at Dorian Restaurant in Notting Hill last Thursday
He or she will also be the 15th great-grandchild of the late Queen Elizabeth II, and the third to be born since her death in 2022.
The new arrival will be the fifth grandchild of Andrew Mountbatten-Windsor, following the birth of Princess Beatrice's daughter Athena Mapelli Mozzi in January last year.
The announcement from Buckingham Palace, which posted the news on its social media channel at 10am, will be seen as a show of support for Eugenie despite the troubles surrounding her father.
Andrew - the King's brother - was arrested on suspicion of misconduct in public office in February amid the scandal surrounding his friendship with the late paedophile financier Jeffrey Epstein.
Eugenie and her sister Beatrice stayed away from the traditional royal gathering on Easter Sunday, with the agreement of Charles, amid the furore over their father.
The princesses, who are granddaughters of the late Queen Elizabeth II, have faced scrutiny themselves after their names appeared in the Epstein files, the US Department of Justice's document dump relating to the convicted sex offender.
One email exchange suggested their mother Sarah took her daughters to see Epstein in the US days after he was released from prison for child sex crimes.
Eugenie and Beatrice were 19 and 20 at the time.
Eugenie (left) and Beatrice (right) after lunch at Soho Mews House in Mayfair last Thursday
Buckingham Palace announces today that Princess Eugenie is pregnant with her third child
Princess Eugenie posted family photos celebrating Jack Brooksbank's 40th birthday yesterday
The former duke and duchess were last seen in public alongside senior members of the Royal Family at the Duchess of Kent's funeral in September last year.
Mr Brooksbank celebrated his 40th birthday yesterday, with the King's niece marking the occasion by sharing photographs on her Instagram story of her husband relaxing on a beach with the caption 'Happy 40th my love'.
The pair married at St George's Chapel in Windsor Castle in October 2018, and welcomed their first child, August, on February 9, 2021.
His younger brother Ernest was born on May 30, 2023.
Eugenie and Mr Brooksbank's announcement comes four days after the Daily Mail published exclusive pictures of the couple out on a date night with friends.
Eugenie is known to be a doting parent who has repeatedly spoken about the joys of motherhood.
But she and her husband of seven years also looked to have thoroughly enjoyed a night without their sons August and Ernest.
The couple, who split their time between a Portuguese villa and a Kensington Palace cottage, affectionately call their boys Augie and Ernie.
The mother of two looked positively glowing in a long, loose, black dress and khaki shirt with Jack wearing jeans, trainers, a dark jacket and a wide grin as they left Dorian Restaurant in Notting Hill.
A photo of Jack Brooksbank in the sand posted by Eugenie yesterday for his 40th birthday
Eugenie also posted an earlier photo with Jack Brooksbank in 2011, a year after they first met
Eugenie's post yesterday featured her son August in the sand with her husband of seven years
Hours earlier, in a rare public appearance together since the Epstein scandal engulfed the House of York, Beatrice and Eugenie chatted animatedly as they walked through Mayfair near Hanover Square.
One witness said they looked 'in great spirits as they made the most of the sunshine'.
The younger York sister led the way carrying a light summer jacket and bag while Beatrice, 37, followed her on a narrow path clutching her mobile phone.
Tourists wandering through London's most exclusive neighbourhood appeared oblivious to the fact they were brushing past royalty.
Their Soho Mews House lunch together last Thursday was the first time the sisters had been seen together in London for six months.
In November, they were spotted hugging each other in the street just hours after their father Andrew was stripped of all his royal titles.
Without their parents, Beatrice and Eugenie joined the Royal Family at Sandringham on Christmas Day as the King showed his support for his nieces.
But as the Epstein scandal swirled once again, and their father was arrested, the pair did not attend the royals' traditional Easter service gathering at Windsor last month.
Neither have been seen with their mother, Sarah Ferguson, or father in recent months.