Boys will be boys even if they are royalty in line to rule England -- like Prince William and Prince Harry.

The British brothers, along with Kate Middleton, apparently engaged in a bit of a water balloon fight while at a Buckingham Palace Garden Party. Roman Kemp, an English radio host, presenter and current contestant on ITV's "I'm A Celebrity... Get Me Out Of Here," spilled all the details.

"One time I had a letter through and it was from Prince Harry to come and DJ at the Buckingham Palace garden party," Kemp explained to his reality castmates in an extra footage scene which appeared on the "I'm A Celebrity" spin-off show, "Extra Camp," according to Cosmopolitan.

"I was playing a track, and someone came over and said 'Roman come here,' and it was Prince Harry. Princess Kate was there, and there was a slingshot in the middle," he shared. "They’ve got a bucket filled with water balloons, and they’re just pinging off these water balloons into the crowd from a balcony."

That's when Kemp revealed Prince Harry wanted him to throw a ballon at Prince William, "I'm like 'what is going on?'. [Harry] said 'aim a bit to the left' and I said 'who am I aiming for?' and he said 'my brother!' I said, 'no I'll be done for treason!'"

READ: Prince Harry Made This Extreme Sacrifice For Prince William Before Royal Feud

The story comes at a time when the royal brothers aren't the closest they've ever been, but it does show that they still share some common ground with humor, which is exactly what body language expert Judy James believed after watching "Harry & Meghan: An African Journey."

"His laugh, when asked about the rumoured rift with his brother William, looked rueful, and he paused to compose his words," she explained. "His grin looked almost like a reflection of what he thought William’s response would be if he were asked the same question and he shoved his hands into his pockets as he told Tom 'I love him dearly' but that they have good days and bad days as brothers."

James continued, "It was clear from his grin that humour is still the tie that binds between them."

Prince Harry and Prince William
Pictured: Prince William and Prince Harry arrive at St George's Chapel at Windsor Castle before the wedding of Prince Harry to Meghan Markle on May 19, 2018 in Windsor, England. Getty Images/Gareth Fuller