Typically well-behaved Princess Charlotte apparently turns into a bit of a wild child when she gets around her favorite cousin Mia Tindall, the eldest daughter of Mike Tindall and Zara Tindall.

Charlotte, who just turned 10 earlier this month, is often the “responsible” one around her brothers Prince George and Prince Louis, according to The Sun—keeping them in line and letting Louis be the mischievous one. But the outlet reported that when the only daughter of Prince William and Kate Middleton gets around 11-year-old Mia, they become “double trouble.”

“Princess Charlotte and Mia Tindall have become best friends—when the cheeky pair are together, that is,” royal biographer and Majesty Magazine editor-in-chief Ingrid Seward told The Sun. “Charlotte is known for being super responsible for both of her brothers, telling them what to do and when to do it at royal occasions. Mia is much more adventurous.”

“But as total opposites, they become as one, as children do when they are together,” Seward added, pointing out that the bond between Charlotte and Mia mirrors that of William and Zara when the latter were younger.

“Prince William and Zara were also partners in crime when they were young,” she continued. “Nannies would dread the two of them being together, as they were super naughty, noisy, and loved getting into trouble. Zara and William are still good friends today.”

Of Charlotte and Mia’s bond, “It makes royal get togethers much more fun, and at their age they can still get away with being cheeky and naughty,” Seward said. “In fact, when they get together, they can be double trouble—but everyone loves them.”

While Charlotte is being raised to likely one day work within the royal fold, Mike and Zara aren’t working royals and give their three kids a deeply “down-to-earth” upbringing, a royal source told The Sun.

Mia walked right alongside the Prince and Princess of Wales, George, Charlotte, and Louis at the royal family Christmas walk in 2023, and a sweet moment between Charlotte and Mia went viral on social media. In the exchange, Mia noticed a member of the crowd assembled was attempting to give Charlotte flowers, to which Charlotte adorably said to her cousin, “You take them” (via People)—and Mia accepted the flowers “with a smile.”

Elsewhere in the day, Mia walked hand-in-hand with Louis, and received flowers from Kate, as well.

After a 2019 playdate between George, Charlotte, and Mia, an onlooker told People that “They are all live wires with loads of energy.” The royal cousins were all on hand for the Platinum Jubilee Parade in June 2022, which Mike said later on an episode of his “The Good, The Bad and The Rugby” podcast was “tough for them. They’re all young. It’s a long time. But as any parents know, you just do whatever needs to be done.”

Per People, Mike admitted of Louis’ particularly hilarious hijinks that day that “Louis, he was just wanting to have fun. And my two [daughters] are always mischievous, so it’s trying to keep a lid on. There were lots of sweets out back though, so there was a real sugar high.”

Zara—who is the daughter of Princess Anne—said earlier this month of life in the royal family, per The Sun, “It is very hard to see from the outside, but 100 percent it is a family that is still going through the same struggles other people do.”

“Whether they are relationships, obviously, it is very easy to see every day,” she continued. “We’re still very supportive of each other.”