The Duke and Duchess of Cambridge have reputations for being particularly devoted parents to their three adorable children. But being devoted apparently doesn't allow a member of the monarchy to slip out of this bizarre 300 year old rule. Prince William and Kate Middleton do not have custody of their kids for an unusual reason, and you would think someone might go ahead and give it an update after 300 years.
Middleton and Prince William are parents to 7-year-old Prince George, 5-year-old daughter Princess Charlotte, and 2-year-old son Prince William. Their children are fourth, fifth, and sixth in the line of succession for the throne, behind their father and grandfather Prince Charles. When Prince Charles does take his place as King of England, he will also take over custody of his grandchildren... all because there is a centuries-old rule written by King George I that sees the reigning sovereign claim legal custody of all minor grandchildren in the royal family. The rule is called the The Grand Opinion for the Prerogative Concerning the Royal Family 1717, enacted by King George I, as per royal expert Monica Koenig, who told Harper's Bazaar, "This goes back to King George I, 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."
Koenig went on to explain that there was a disagreement between King George I and his son over who would be a godparent to one of his children, so the king had a rule enacted to make him the guardian. And it has stood for more than 300 years without change. Custody in this case means that the sovereign is in charge of making decisions regarding travel, education, and their eventual marriage.
This rule means that Prince Charles would also be legal guardian to Prince Harry and Meghan Markle's 17-month-old son Archie once he becomes king, although the fact that they have stepped down from their senior royal roles could well put that custody into question.
Queen Elizabeth might not be the legal guardian of the Cambridge kids simply because King George I didn't have great-grandchildren and therefore they were not written into the rule. However she was legal guardian to Prince William and Prince Harry, which became a slight issue for their mother Princess Diana after she and Prince Charles were divorced in 1996. At the time of the divorce a statement was released announcing that Princess Diana would "continue to be involved in all decisions relating to the children" but the Sun reports that she was not able to travel to Australia with her sons before her death as the Queen did not give permission.
Fortunately for all parents involved, the rule is considered something of a formality. Because how weird would that be?