The King shared a rare personal message to mark his first cousin once removed the Duke of Kent's 88th birthday on Monday.
The image posted on the royal family's official social media accounts shows the Duke at the Chelsea Flower Show last year, surrounded by greenery, white roses and pastel-hued buds.
"Wishing a very happy birthday to The Duke of Kent today" the caption read.
Prince Edward (the Duke of Kent) is the first cousin of the late Queen Elizabeth, and the pair remained close until her death in September 2022.
The Duke accompanied Her Late Majesty to Trooping the Colour in the quadrangle at Windsor Castle in 2021, when there was a reduced ceremony due to the pandemic.
He also stood alongside the late Queen to receive the salute from the balcony at Buckingham Palace during her Platinum Jubilee celebrations in June 2022.
As a first cousin of Queen Elizabeth II, it makes him a second cousin to King Charles.
Prince Edward George Nicholas Paul Patrick was born on 9 October 1935 in London as the eldest child of the late Prince George and Princess Marina of Greece and Denmark. He also has two younger siblings, Princess Alexandra, 86, and Prince Michael of Kent, 81.
Edward has held the title of Duke of Kent since the age of six, after the tragic death of his father in a plane crash in 1942.
In June 1961, he married Katharine Worsley at York Minster with the bride wearing a wedding dress designed by John Cavanagh. Katharine also secured her veil with the Kent Diamond and Pearl Fringe Tiara.
The Duchess, who taught music at a primary school in East Hull, co-founded charity Future Talent, which helps gifted young musicians from low-income backgrounds flourish.
She has kept a low-profile since stepping back from royal duties in 1996 and six years later, she made the personal decision not to use the style "Her Royal Highness," famously telling the BBC, "Call me Katharine".
Edward and Katharine have three children, George Windsor, Earl of St Andrews, Lady Helen Taylor and Lord Nicholas Windsor, born in 1962, 1964 and 1970 respectively.
The Kents, who split their time living between Wren House Kensington Palace and Oxfordshire, also have ten grandchildren.
Edward, who is 41st in line to the throne, is still a full-time working royal and is involved with over 140 charitable organisations.
He was one of the senior working royals to appear on the balcony at the King and Queen's coronation in May, and Charles's first Trooping the Colour parade in June.
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