Prince William is officially 41 years old, and his family is celebrating him, including the king. On Wednesday, King Charles shared a new photo of William at the coronation, giving us a behind the scenes look at their father and son relationship in the never-before-seen pic.

Charles wished William a happy birthday on Instagram.

View this post on Instagram A post shared by The Royal Family (@theroyalfamily)

The royal family’s official Instagram account shared this photo of Charles and William at the coronation rehearsal, where the father and son seemed to be sharing a chuckle during what was practice for an otherwise very formal and somber ceremony.

“Wishing The Prince of Wales a very happy birthday today!” read the caption, which included a red balloon emoji.

This is Will’s first birthday as the Prince of Wales.

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After Queen Elizabeth’s death in September, William and wife Kate Middleton were given the titles of Prince and Princess of Wales — the first to hold them since Princess Diana and the former Prince Charles.

This is the first birthday he’s celebrating since his beloved grandmother’s death, which means it’s also the first with his new responsibilities.

Westminster Abbey also participated in a birthday tradition for Will.

Wishing HRH The Prince of Wales a very happy birthday today! The Abbey bell ringers are ringing 541 changes of Stedman Caters followed by a course of London Surprise Royal in celebration. pic.twitter.com/WcLuYQ3V3j — Westminster Abbey (@wabbey) June 21, 2023

The Westminster Abbey bells only ring for the king and his heir — which would be Prince William, of course — making this a particularly special honor.

The abbey’s official Twitter account shared a video of the bells ringing, writing, “The Abbey bell ringers are ringing 541 changes of Stedman Caters followed by a course of London Surprise Royal in celebration.”

King Charles has a busy week.

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Not only is it Will’s birthday, but also he and Camilla are at Royal Ascot, the horse racing event that is going on all week. Will and Kate are expected to attend later this week, but on Wednesday, Charles and Camilla were joined by fellow royals Prince Edward and his wife, Sophie.

There’s no doubt Will’s birthday will be a special one.

View this post on Instagram A post shared by The Prince and Princess of Wales (@princeandprincessofwales)

After all, Kate is known for going all out for their three children’s birthdays — homemade cake included — so it seems certain that she’ll do the same for her husband, even though 41 isn’t the same milestone birthday he celebrated last year.

Happy birthday, Will!