Why Prince William and Kate Middleton don't have full custody of their children

Prince William and Kate Middleton are often sharing sweet anecdotes about their three children, Prince George, Princess Charlotte and Prince Louis. Whether it's George's favourite hobby, Charlotte's adorable nickname or Louis' hilarious first word and love for Mary Berry, royal fans love to hear about the Cambridges lives behind closed doors.

And while they're considered to be very modern in their parenting approach, opening up about how they discipline their children and ripping up the royal rule book on occasion, according to a report from news.com.au, royal parents do not have full custody of their little ones.

A law was passed in 1717 and legislated in 1772 which means that the sovereign actually has legal custody of their minor grandchildren.

Royal expert Marlene Koenig explains: 'The sovereign has legal custody of the minor grandchildren.

'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.'

So what exactly does this mean for young royals?

The reigning monarch will have a say in the child's upbringing, travel and education. The law states they are in charge of their 'education and care', 'ordering the place of their abode', 'appointing their governors and governesses' and 'the care and approbation of their marriages.

The Queen had custody of William and Harry when they were minors. But as King George I didn't have great-grandchildren when the law was passed, it is unclear whether or not this currently applies to George, Charlotte and Louis.

However, when Prince Charles takes the throne, the law will dictate that he will then have custody of the three little royals as they are his grandchildren.

Who knew!