Prince Harry told mourners that Windsor Castle is a "lonely place up there now without her" as he marked the Queen's death.
Prince William is understood to have personally invited his brother and sister-in-law Meghan to join him and Kate outside the royal estate to greet the crowds and read tributes this afternoon.
It was the first time the four of them - dubbed the 'Fab Four' - have been seen together in public since early 2020, prior to the Sussexes stepping down as working royals.
But they appeared to have put any differences aside to honour Elizabeth II and take time out to meet members of the public.
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Having been asked what the Berkshire estate was like now without Her Majesty, Harry's response was filmed, with the footage then obtained by the Sun.
He added: "Every room she was in, we felt her presence throughout."
The two couples exited separate vehicles but walked side to by side before spending over 40 minutes meeting fans.
They looked over the flowers and messages left for the Queen - who died on Thursday - along the gates as the crowds roared.
It had been suggested the foursome had not spoken since Harry and Meghan arrived in the UK a week ago, despite staying less than a mile apart at Frogmore and Adelaide Cottages.
The Sussexes arrived holding hands and continued to do so at various stages of the proceedings.
All four royals, dressed in black, bent down to look at some of the many tributes left in front of the gates.
Meghan and Harry were seen chatting, but they kept a slight distance away from William and Kate.
At one point, William crouched down to read some of the messages that had been left on the cards.
Meghan rubbed Harry's back reassuringly before linking arms with him as they looked at more of the flowers.
At the end, the brothers got close and started talking to one another as they walked to greet some of the well-wishers.
But they went separate ways and went to speak to people on different sides of the road.
Royal journalist and Harry and Meghan's biographer Omid Scobie said William - now the Prince of Wales - made the decision to invite the Sussexes "in the eleventh hour".
He said: "The Waleses had always been scheduled to greet well-wishers at Windsor Castle, but royal sources say the decision to invite the Sussexes was made in the eleventh hour.
"It is, without a doubt, a significant moment in the history of the relationship between the two brothers."
In another tweet, he added: "After chatting, hugging and sharing sympathies with members of the public for over 40 minutes, the Prince and Princess of Wales and the Duke and Duchess of Sussex have headed back into the Windsor Estate together.
"Both couples left in the same car, driven by William."
The Prince of Wales - who is also now the Duke of Cornwall and Cambridge - drove at least part of the way to Balmoral on Thursday, with royals including Prince Andrew as passengers.
* This weekend, the Daily Mirror and Sunday Mirror celebrate the life of Her Majesty the Queen with a commemorative special filled with all the key moments from Britain’s longest reigning monarch.
Be sure to pick up your copy of the Daily Mirror and Sunday Mirror to get both pullouts.
