Kate took the photo on an iPhone during a visit to Cumbria earlier this year.
A photo of her younger brother, Prince Louis, was also released through social media just over a week ago.
The image, taken by the Princess of Wales, was shared on 23 April to mark the young royal’s seventh birthday.
Prince George, William and Kate’s eldest child and the second in line to the throne after his father, will turn 12 on 22 July.
Last week, the Prince and Princess of Wales visited the Isle of Mull in Scotland to celebrate their 14th wedding anniversary.
Meanwhile, the King recently reflected on his “frightening” experience of his cancer diagnosis after a difficult year for the Royal Family.
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