King Charles shared a candid, never-before-seen photo with Prince William to celebrate his son's birthday

• Prince William turned 41 on Wednesday.
• The royal family shared a candid photo of the prince and King Charles on its Instagram to celebrate.

King Charles gave a glimpse into his relationship with Prince William in a never-before-seen photo.

On Wednesday, the Prince of Wales turned 41, marking his first birthday since he was created with his father's long-held title.

The king celebrated the occasion with an Instagram post for his eldest son.

The royal family Instagram account shared a photo of the king and William laughing at a rehearsal for Charles' coronation at Westminster Abbey, which took place on May 6. Royal photographer Chris Jackson captured the shot.

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A post shared by The Royal Family (@theroyalfamily)

"Wishing The Prince of Wales a very happy birthday today!" read the caption.

Prince William played a key role in his father's coronation, kneeling before the king to pay homage to him as he was crowned monarch.

The king's birthday tribute to William marked a different approach to the heir-to-the-throne's birthday as compared to Queen Elizabeth's.

In the years before her death, the royal family Instagram did not acknowledge the king's birthday on its Instagram with a post.

Although he is less than a year into his reign, King Charles has already showed signs of embracing a more modern approach to the throne than his mother did.

For instance, the king had a scaled-down coronation compared to Queen Elizabeth, with only 2,200 guests invited instead of around 8,000. And after he ascended, he invited faith leaders from multiple religions to Buckingham Palace on September 16, 2022, and told them he considered it his duty to "protect the diversity of our country," which was a bold move for the leader of the Church of England.

The royal family also held King Charles' official birthday celebration at the Trooping the Colour over the weekend, despite the fact that he was actually born in November.

William and Kate Middleton, the Princess of Wales, attended the celebration and appeared on the balcony at Buckingham Palace with their children: Prince George, Princess Charlotte, and Prince Louis.

Prince Louis was photographed making several funny faces during the appearance, which has become a bit of tradition for him at royal engagements.