Prince William and Prince Harry, accompanied by their wives Catherine and Meghan, have made their first public appearances since the death of the Queen, greeting wellwishers outside Windsor Castle.
It was also the first time the two couples had been seen together since the Prince Harry and Meghan's highly publicised withdrawal from royal life after a series of controversies.
The appearance came shortly after the Prince of Wales released a statement pledging his support to King Charles III "in every way I can" and hailing "our extraordinary Queen".
Earlier on Saturday was the first public appearance of the Queen's youngest children — Princess Anne, Prince Andrew and Prince Edward – who also thanked wellwishers outside Balmoral Castle.
But it was the public display of unity between the two brothers and their spouses outside Windsor Castle that might have surprised many.
The couples were driven down from the castle to the castle gates at the start of the Long Walk, before disembarking two four-wheel drives and walking together to view tributes to the late Queen.
Crowds initially cheered their appearance before a hush fell over them, and the members of the royal family read notes and looked at flowers left at the gates.
The two couples then turned to the crowd, who in turn erupted in cheers for them, as they moved over to speak to those lined along barriers.
The Prince and Princess of Wales took to one side of the Long Walk while the Duke and Duchess of Sussex took the other, receiving flowers and shaking hands.
Prince William was heard telling someone in the crowd that the days following his grandmother's death had been "surreal".
"We all thought she was invincible," he said, according to Reuters.
After about 40 minutes speaking with members of the public, the two couples then left in the same car, which was driven by Prince William.
A spokesman for the Prince William said he had invited the Duke and Duchess of Sussex to join him and and Princess of Wales as they viewed the flowers and spoke to wellwishers.
Prince William pledges to support King, hails Queen
Shortly before his appearance, Prince WIlliam released a heartfelt written tribute to his grandmother, saying he was "incredibly grateful" to have had the Queen's wisdom and reassurance.
"On Thursday, the world lost an extraordinary leader, whose commitment to the country, the Realms and the Commonwealth was absolute," he said in a statement released by Kensington Palace.
"So much will be said in the days ahead about the meaning of her historic reign.
"I, however, have lost a grandmother. And while I will grieve her loss, I also feel incredibly grateful.
"I have had the benefit of the Queen's wisdom and reassurance into my fifth decade."
The 40-year-old heir to the throne said the Queen "was by my side at my happiest moments".
"And she was by my side during the saddest days of my life.
"I knew this day would come, but it will be some time before the reality of life without Grannie will truly feel real."
Family can 'now start process of handing her on'
Earlier on Saturday, Prince Andrew thanked people for paying their respects at Balmoral Castle, saying his family could "now start the process of handing her on".
The Duke of York was joined by his sister Princess Anne and brother Prince Edward, along with members of their families, for their first public appearance since the death of Queen Elizabeth II.
The group had left Crathie Kirk – a small church used as a place of worship for the royal family when at Balmoral – and travelled in a convoy back to the palace gates after a private service was held.
They then left their vehicles a short distance from the entrance to Balmoral to speak to the crowd.
It was the first time Prince Andrew had spoken publicly since he settled a multi-million-dollar lawsuit with Virginia Giuffre, who had accused the duke of sexually abusing her when she was 17.
Speaking to a member of the public, he said: "We've been allowed one day, now we start the process of handing her on," the Press Association reported.
Joining the three siblings were the Queen's four granddaughters: Princess Eugenie and Princess Beatrice, Zara Tindell and Lady Louise Windsor.
Her eldest grandson, Peter Philips, was also there alongside Timothy Lawrence, the Princess Royal's husband, as well as Prince Edward's wife Sophie, the Countess of Wessex.
The group stopped along the walk to speak to members of the public, before stopping to view floral tributes and notes left by members of the public outside the castle gates.
Prince Andrew was seen putting an arm around his daughter Princess Eugenie to comfort her as she viewed the tributes.
Princess Eugenie was also seen laying flowers alongside other tributes.
Before heading back into the castle grounds, the group turned around and waved to thank those who had come out to mourn.
