The Duke and Duchess of Cambridge have a few unconventional hurdles to leap when parenting their three children George, Charlotte and Louis. And the same rule may apply to Harry and Meghan.

First, there’s the insatiable paparazzi, always keen to snap the children on their way to school.

Then there are the many confusing royal etiquette rules. After that, there are the official royal events, which weren’t exactly planned with rambunctious toddlers in mind.

And then, finally, there’s the unusual custody arrangement with the Queen.

Even the most knowledgeable fan might not be aware of this, but according to royal historians, Prince William and Kate Middleton don’t have legal custody of their own children. That, in fact, belongs to the children’s 92-year-old great-grandmother, Queen Elizabeth II.

“The sovereign has legal custody of the minor grandchildren,” royal expert Marlene Koenig told

“This goes back to King George I [who ruled in the early 1700s], and the law’s never been changed. He did it because he had a very poor relationship with his son, the future King George II, so they had this law passed that meant the King was the guardian of his grandchildren.”

The law is more than 300 years old and was passed by a majority of 10 out of 12 judges in 1717, who decided the monarch’s “right of supervision extended to his grandchildren and this right of right belongs to His Majesty, King of the Realm, even during their father’s lifetime”.

According to Koenig, who has written two books on the history of the British royal family and had dozens of articles published in the “Eurohistory Journal,” the law was legislated once again in 1772, when King George III was in power, and has never has been superseded by new legislation.

The custody law still stands today, and over recent decades has affected the way the royals parent their children, especially when it comes to matters of upbringing, travel and education.

“When [Princes Harry and William] were little, Prince Charles asked the Queen if both children could fly on a plane together to Scotland, to which the Queen said yes,” Koenig said.

“Technically, they needed permission for travel. The Queen has the last word on parenting decisions like that.”