Queen Elizabeth II has no legal custody of her great-grandchildren, claims one source.

It was reported earlier that Her Majesty has custody of Prince William and Kate Middleton's children, Prince George, Princess Charlotte and Prince Louis. Prince Harry and Meghan Markle will also reportedly not have custody of their children because the rights belong to the monarch. However, according to Joe Little, managing editor of Majesty, this is not true.

"This isn't an Act of Parliament, but a royal prerogative established in the early 18th century, so it is not legally binding," Little told People about the 300-year rule that triggered the debate over who the legal custody of the minor royals belongs to.

"It is nothing more than a royal prerogative and is archaic and would have little bearing today," Little continued. "The circumstances would have to be pretty extreme for the Queen to invoke it on behalf of her great-grandchildren. Given that there are parents, and grandparents alive – not to mention all the aunts and uncles – there is a huge support structure already in place for the great-grandchildren."

The publication noted that the Queen has no legal authority over her minor great-grandchildren. However, she can give her input on any major parenting decisions. For instance, the monarch has the last say regarding the two heirs traveling together on the same plane.

There's an unwritten royal protocol that forbids the heirs to board the same flight to protect the lineage. However, Prince William and Middleton already broke this with the Queen's approval of course when they took Prince George to an overseas royal engagement. The Duke and Duchess of Cambridge are expected to break the same rule by traveling with Prince Luis abroad.

The legal custody of the minor royals became a subject of interest after royal historian Marlene Koenig opened up about it and claimed that it belongs to the Queen.

"The sovereign has legal custody of the minor grandchildren," Koenig told News.com.au. "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."