Prince Charles has paid a sweet tribute to his sister Princess Anne to mark her 71st birthday. The Prince of Wales and his wife the Duchess of Cornwall shared a black and white photograph from his childhood to commemorate the occasion, delighting royal fans with the adorable throwback.
DISCOVER: 6 of Princess Anne's funniest moments as she celebrates her birthday
The image in question sees a young Charles leaning over a bonnet-clad Anne in her pram, clutching her hand as she smiles at him.
The post, shared on the official Clarence House Instagram account, was captioned: "Wishing The Princess Royal a very Happy Birthday today.
WATCH: Princess Anne pays moving tribute to Duke of Edinburgh
"In this photo from 1951, The Prince of Wales squeezes his younger sister’s hand while sitting in their prams in the Clarence House garden."
THROWBACK: Prince Charles shares heartwarming childhood photo with the Queen, Prince Philip and Princess Anne
Royal fans were thrilled by the sweet tribute, with one writing: "What a lovely photo! Wishing this wonderful lady a very happy birthday".
Another shared: "Awh, what a lovely photo", while hundreds of others expressed their well-wishes to the Princess Royal on her birthday.
The Prince of Wales and his younger sister are only two years apart in age and have shared a close relationship from an early age.
BEST PHOTOS: 10 sweet photos that show Prince Charles and Princess Anne's close sibling bond
The pair have also been present for key moments in one another's lives, such as Charles' investiture as the Prince of Wales in 1969, Anne's participation in the 1976 Olympics in Montreal and their respective weddings.
Last year, three striking portraits were released by Buckingham Palace to mark the Princess Royal's 70th birthday.
Princess Anne and Prince Charles have always been close
It's not known whether Anne, who carries out hundreds of royal engagements each year, has joined the Queen at her Balmoral estate yet this summer.
Princess Anne Elizabeth Alice Louise was born on 15 August 1950 at Clarence House, as the second child of the Queen and the late Duke of Edinburgh.
RELATED: Princess Anne's surprising residents at sprawling estate revealed
She was educated at Benenden School in Kent and left with six GCE O-Levels and two A-Levels. She began to carry out royal engagements in 1969 at the age of 18 and she was the first member of the royal family to compete in the Olympics in Montreal in 1976.
Make sure you never miss a ROYAL story! Sign up to our newsletter to get all of our celebrity, royal and lifestyle news delivered directly to your inbox.