Prince Harry's new memoir divulges family secrets as well as addresses rumors that have plagued the British royal family for some time.

In his book, "Spare," Harry tackles the long-running joke that he is not the biological son of King Charles III.

"'Who knows if I'm really the Prince of Wales? Who knows if I'm even your real father? Maybe your real father is in Broadmoor, darling boy,'" Harry writes his father would joke, per NBC News.

"Pa liked telling stories, and this was one of the best in his repertoire," Harry added of this particular narrative.

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Prince Harry in a dark suit and tie on the red carpet split King Charles in a pin-striped suit and tie

Prince Harry discussed the running rumor that he was not the son of King Charles. (Mike Coppola/Ian Vogler)

Although the Duke of Sussex writes that his father would "laugh and laugh" at the rumors, Harry found it to be "a remarkably unfunny joke, given the rumor circulating just then that my actual father was one of Mummy's former lovers: Major James Hewitt." 

The late Princess Diana and Hewitt had an affair while she was still married to King Charles, something the former Princess of Wales later confirmed in a 1995 interview with the BBC.

James Hewitt in a light blue button down shirt soft smiles

James Hewitt has often been thrown into the conversation by tabloids discussing who Prince Harry's "real father is." (Yui Mok - PA Images)

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"One cause of this rumor was Major Hewitt's flaming ginger hair, but another cause was sadism," Harry writes. "Tabloid readers were delighted by the idea that the younger child of Prince Charles wasn't the child of Prince Charles. They couldn't get enough of this 'joke,' for some reason. Maybe it made them feel better about their lives that a young prince's life was laughable."

Prince Harry clarified any confusion, definitively explaining, "Never mind that my mother didn't meet Major Hewitt until long after I was born, the story was simply too good to drop." 

King Charles in a tuxedo poses with his son Prince Harry on the steps of the National History Museum in 2019

King Charles reportedly laughed at rumors he wasn't Prince Harry's biological father. (Samir Hussein/WireImage)

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In 2002, during an interview with the Sunday Mirror, Hewitt himself refuted claims he was Harry's father.

"There really is no possibility whatsoever that I am Harry's father. I can absolutely assure you that I am not," he said at the time.

"Admittedly the red hair is similar to mine and people say we look alike. I have never encouraged these comparisons and although I was with Diana for a long time I must state once and for all that I'm not Harry's father. When I first met Diana, Harry was already a toddler," he noted.