Prince Harry and Meghan Markle joined Prince William and Kate Middleton for an impromptu walk to view tributes to Queen Elizabeth II

• Prince Harry and Meghan Markle joined Prince William and Kate Middleton for a walk on Saturday.
• The couples stepped out in all-black to view tributes to Queen Elizabeth II, who died Thursday.

Prince William and Kate Middleton were joined by Prince Harry and Meghan Markle on a stroll around Windsor Castle Saturday to view tributes to Queen Elizabeth II.

The Queen passed away at the age of 96 on Thursday at her Scottish home of Balmoral, bringing her lengthy reign to a close. William, Kate, Harry, and Meghan stepped out to view floral tributes to the late monarch and greet onlookers in all-black outfits.

Sources told People that security didn't expect all four royals to walk around the property, adding that William thought the walk would be an important show of unity. Entertainment Tonight reports that William reached out to Harry an hour before their promenade and asked if he and Meghan would like to join them.

Both couples are currently staying at Windsor Castle, ET writes. This is the first time the couples have been seen together publicly since the Queen's death earlier this week.

Representatives for the Duke and Duchess of Sussex and the Prince and Princess of Wales did not immediately respond to Insider's request for comment.

Earlier in the day, William released his first statement on the death of his grandmother on his joint Instagram account with Kate. The royal wrote that he feels "incredibly grateful," even as he grieves his "Grannie."

"I knew this day would come, but it will be some time before the reality of life without Grannie will truly feel real," William wrote. "I thank her for the kindness she showed my family and me. And I thank her on behalf of my generation for providing an example of service and dignity in public life that was from a different age, but always relevant to us all."

The Duke and Duchess of Sussex also paid tribute by writing "In Loving Memory of her Majesty Queen Elizabeth II" in a brief statement on their official Archwell organization.

The relationship between the Prince and Princess of Wales and the Duke and Duchess of Sussex has been widely reported on since Meghan married into the royal family in 2018. Following Harry and Meghan's "step back" from royal life in January 2020 and explosive interview with Oprah Winfrey the following year, Insider's Mikhaila Friel wrote that the couple's relationship with Harry's royal relatives still appeared fraught.

At Prince Philip's funeral in April 2021, the brothers were photographed chatting with each other for the first time since the interview.