He's gene deficient.

Prince Harry Reportedly Writes About Those James Hewitt Rumors in His MemoirStory by Lauren Hubbard
Jan. 6, 2023
American audiences may not recognize James Hewitt's name in season four of The Crown, but the military man is at the heart of one of the biggest scandals to besiege the monarchy in the late 20th century. Here's everything you need to know. ...
Not long after he became Diana's riding instructor, the two became romantically involved—an arrangement that would last for several years. The Princess's marriage to Prince Charles was known to be rocky by the time she met Hewitt, and Charles was reportedly already carrying on his own liaison with his former girlfriend (and future wife) Camilla Parker-Bowles, which Diana's bodyguard, Wharfe, posited may have contributed to her willingness to begin an affair with Hewitt. ...
As a consequence of Hewitt's romance with Diana, fans have frequently speculated that Hewitt could, be the father of Prince Harry, citing a resemblance between the two—their red hair, in particular. Hewitt has uniformly denied these claims. Likewise, Wharfe wrote, "A simple comparison of dates proves it is impossible for Hewitt to be Harry’s father.... Harry was born on September 15, 1984, which means he was conceived around Christmas 1983, when his brother, William, was 18 months old. Diana did not meet James Hewitt until the summer of 1986." ...
Prince Harry reportedly writes in Spare that King Charles joked about his parentage.
"Pa liked telling stories, and this was one of the best in his repertoire. He’d always end with a burst of philosophizing … Who knows if I’m really the Prince of Wales? Who knows if I’m even your real father?" he writes, according to a leak obtained by Page Six. "He’d laugh and laugh, though it was a remarkably unfunny joke, given the rumor circulating just then that my actual father was one of Mummy’s former lovers: Major James Hewitt. One cause of this rumor was Major Hewitt’s flaming ginger hair, but another cause was sadism."
Charles, Harry writes, never spoke to him about the Hewitt rumors. He also writes that though the tabloids loved the idea, "Maybe it made them feel better about their lives that a young prince’s life was laughable. Never mind that my mother didn’t meet Major Hewitt until long after I was born." ...
Town and Country via MSN