Rare Footage Shows King Charles as a 'Very Sincere' Father, Director Says of New Doc (Exclusive)

See PEOPLE's exclusive sneak peek of the new National Geographic special Charles: In His Own Words

King Charles' royal role as a father has been among his most scrutinized, and a new documentary is zooming in on why — and debunking common conceptions.

Prince William and Prince Harry will both attend their dad's historic coronation on May 6, and National Geographic is releasing a new special with never-before-seen and rare archival footage ahead of the crowning ceremony. PEOPLE shares an exclusive sneak peek of Charles: In His Own Words below, which follows the monarch from young adulthood to the present.

Throughout the research process, director Tom Jennings says that King Charles' love for his sons was a clear theme.

"I was surprised. We found that great footage of him in '93, '94, with his sons at a loch in Scotland, running around in a kilt and roughhousing with his boys. And then we found several interviews from him that weave throughout there, and it paints an endearing portrait of him as a father. Listening to what he said hoped for his sons as they were growing up, I found those words to be very sincere," Jennings tells PEOPLE.

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"I don't think that they were put on at all, I think he really meant it. And when you see images like that, and then know how things have turned out to this point, to me it felt very sad. That this is what once was," he adds.

The Emmy Award-winning director chronicled Charles' life story in his signature first-person narrative, the same documentary style in which he examined Princess Diana in Diana: In Her Own Words (2017) and Queen Elizabeth in Being the Queen (2020). Jennings says that while he and his team "just tried to tell a story down the middle journalistically" with Charles: In His Own Words, it's understandable why the royal dad mostly kept his relationships with Prince William, now 41, and Prince Harry, now 38, outside of the spotlight while they were growing up.

"It's not his job to be parading around his relationship with his young sons to the world, for the world to see what a great father he is. And he had a pretty rough childhood as well, which is reflected in our film. He could never live up to what Prince Phillip wanted him to be," Jennings says of Charles' complicated relationship with his own father.

"Everything he does — from a leaky pen to riding in the back of a car with a mystery woman who turned out to be Queen Camilla — it's always photographed. It's always studied, it's always amplified," he continues.

The camera can only show so much, and Jennings says that the King, 74, did his best in raising his kids.

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"I think the truth always lies somewhere in the middle. And was he completely warm and giggly all the time? No. Was he absent like his own father was? Most likely not," the director tells PEOPLE. "I think he probably did what he could. And when he was doing those things, it looked like they were having a pretty good time."

Charles: In His Own Words premieres on National Geographic on Friday, April 28 at 10 p.m. ET. The special hits Hulu on Saturday and debuts on Disney+ on Friday, May 5.

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