King Charles shares glimpse into his childhood in birthday post to Princess Anne

King Charles III shared a glimpse into his childhood as he marked his sister Princess Anne's 73rd birthday.

On Tuesday, the royal family's account on X, formerly Twitter, posted a photo from the Royal Trust Collection showing the 74-year-old monarch and the Princess Royal as infants as well as a never-before-seen image of the pair on coronation day.

"Wishing Her Royal Highness The Princess Royal a very Happy Birthday today!" the account tweeted.

King Charles III shared a glimpse into his childhood as he marked sister Princess Anne's 73rd birthday. (Chris Jackson/Getty/The Royal Trust Collection/Royal Family Twitter)

The black and white childhood snap was taken at Clarence House in July 1951 when Charles was 2 years old and Anne was 11 months. In the photo, the siblings were seated side by side in matching prams as Charles leaned over and held his little sister's hand.

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The future king was dressed in pajamas that featured a Peter Pan collar, and the princess was clad in white with a matching ruffled baby bonnet.

In the behind-the-scenes photo from the king's grand occasion May 8, the siblings shared a smile. Charles was wearing his full royal regalia, including the Robe of Estate and the Imperial State Crown. 

Anne, who played a special role in the coronation as the "Gold Stick in Waiting," wore a Royal Navy military uniform. The Gold Stick in Waiting traditionally acts as the king's bodyguard and personal protector.

After Charles and wife Queen Camilla were crowned, Anne rode on horseback behind the couple in the Golden Coach and led a procession of 6,000 armed services personnel to Buckingham Palace.

Anne, who has been called the "hardest working royal," turned 73 Aug. 15 (STF/AFP via Getty Images)

Anne is an expert equestrian who began competing at age 11. In 1976, she became the first royal to compete in the Olympic Games. She rode mother Queen Elizabeth II's horse Goodwill on the equestrian team during a three-day event at the Montreal Olympics.

During an interview with CBC, the princess joked about one particular benefit of serving as the Gold Stick.

"I have a role as the colonel of the Blues and Royals in the Household Cavalry regiment as Gold Stick," she told the outlet. "And Gold Stick was the original close protection officer. So, that is a role I was asked if I'd like to do for this coronation, so I said yes.

"Not least of all, it solves my dress problem."

Charles gave Anne a special role in his coronation as the "Gold Stick in Waiting." (Chris Jackson/Getty Images)

Royal sources reportedly told the Mirror that Charles personally expressed his wish for her to take on the role, and she was "incredibly honored."

"The direction of the king’s decision is clear for all to see," a Buckingham Palace insider said. "He is rewarding the princess royal for her loyalty and her unwavering devotion to duty above all else. 

"The king values his sister as a trusted lieutenant, and this is the perfect example of such a relationship," the source noted. 

The Gold Stick in Waiting is traditionally the king's bodyguard and personal protector. (Dan Mullan/Getty Images)

Though Anne has never served in the military, she does hold a number of titles affiliated with the British armed forces.  

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In 1993, the royal was given the ceremonial rank of rear admiral in the Royal Navy and later promoted to vice admiral in 2009 and then to admiral in 2012. 

Last week, Anne and eight other members of the working royal family received new military appointments. (Hugo Burnand/Buckingham Palace)

In honor of her 70th birthday in 2020, the late Queen Elizabeth promoted her to general in the British Army and air chief marshal in the Royal Air Force. 

Last week, Anne and eight working members of the royal family were given new military titles by Charles. Anne became deputy colonel-in-chief of the Royal Regiment of Scotland, a role Buckingham Palace said was to recognize "her royal highness’s strong links to Scotland" as well as her existing ties as the colonel-in-chief of the 1st Battalion, The Ranger Regiment and 6th Battalion, The Royal Regiment of Scotland.

Anne is married to retired navy officer Vice Admiral Timothy Laurence. The pair married in 1992, the same year Anne finalized her divorce from first husband Captain Mark Phillips. The princess and Phillips, who were married for 19 years, share son Peter Phillips, 44, and daughter Zara Tindall, 41.

Ashley Hume is an entertainment writer for Fox News Digital. Story tips can be sent to This email address is being protected from spambots. You need JavaScript enabled to view it. and on Twitter: @ashleyhume