The post also included pictures of Charles with his father
On Father's Day, King Charles III shared a heartwarming photo of himself with his sons, Prince William and Prince Harry.
The caption of the post reads, "To Dads everywhere, we wish you a very special Father's Day today."
The post also included pictures of Charles with his father, the late Prince Philip, and Queen Camilla with her late father Bruce Shand.
King Charles's picture with Prince Harry and Prince William was taken on August 16, 1997, about two weeks before they lost Princess Diana, Page Six reported. Harry and William were on holiday with their father at Balmoral Castle in Scotland at the time.
They were due to meet up with their mother on August 31 - the day she was killed in a car crash alongside Dodi Fayed in Paris, the report said.
The symbolic pictures come on the heels of a rocky time between Charles and his youngest son, Prince Harry.
Meanwhile, Prince Harry recently addressed the longstanding rumour that King Charles III is not his real father, adding that the claim caused him great pain over the years.
Prince Harry noted that several newspapers had reported a rumour that his biological father was James Hewitt after his mother admitted to having an affair with him.
In the witness statement, Prince Harry reiterated the false nature of the rumours, citing the fact that his mother's affair with James Hewitt didn't start until years after he was born.
"Never mind that my mother didn't meet Major Hewitt until long after I was born, the story was simply too good to drop," he said in the written statement.
''At the time, when I was 18 years old and had lost my mother [Princess Diana] just six years earlier, stories such as this felt very damaging and very real to me,'' Harry said.
''They were hurtful, mean, and cruel. I was always left questioning the motives behind the stories. Were the newspapers keen to put doubt into the minds of the public so that I might be ousted from the Royal Family?", he added.