The official Instagram account of the Danish royal family shared two images of the 16-year-old to mark the monumental occasion. Both photos, taken by photographer Steen Brogaard, were taken at Herlufsholm boarding school, south of Copenhagen.

The royal had just started his secondary studies at the prestigious boarding school in September.

The caption reads: “His Royal Highness Prince Christian celebrates his birthday and turns 16 today.”

“The Prince is celebrating his day with his family, and on the anniversary, the Crown Prince and Crown Princess are pleased to share new images of Her Royal Highness.”

The images sent royal fans into a frenzy as well-wishers filled out the comments section, with many noting the similarities between the prince and his mother, Crown Princess Mary.

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Another user, Tony, was shocked at the prince’s age.

“I can’t believe Mary’s little boy is 16 !! Where have the years gone? they wrote.

Crown Prince Frederik and Crown Princess Mary have four children together: Prince Christian, Princess Isabella, Prince Vincent and Princess Josephine.

Christian is the second heir to the Danish throne after his father, Crown Prince Frederik.

The prince was born in 2005 in Rigshospitalet, the university hospital in Copenhagen, as the first Danish royal heir born since his father Crown Prince Frederik in 1968.