And secrets don't get much bigger than this one...
The Royals are the most influential family in the UK – that’s a fact, and with Kate and Wills welcoming their third child this year, the Cambridges are undoubtedly the most talked-about household in the family tree.
But while the Duke and Duchess of Cambridge welcome us into their life as a couple, when it comes to their children they are a lot more protective.
The couple share photographs of their children and bring them along to official events, but both Kate and Wills have stressed their want for their children to be children, allowing them time to enjoy life before they assume the drawbacks attached to their royal status, responsibility and duty.
It was revealed this week in fact, that five-year-old Prince George, third in line to the throne behind his father and grandfather, is still not aware that he is a future King.
And why? Apparently it’s all down to Prince William’s past experience.
The Duke has often been referred to as a ‘reluctant King’, reportedly previously struggling under the magnitude of the role he was born into – and aware of from such a young age.
This is something that Catherine Mayer, author of Charles: The Heart of a King, knows all too well, explaining how Kate and William will use that past experience to introduce their children to their roles gradually.
‘With George they are trying to delay that moment of realisation and give him normality before they thrust this on him,’ Mayer explained in an interview with E! News.
‘But it will be, nevertheless, part of his upbringing both in terms of what he sees his parents and grandparents doing and probably quite soon a beginning of an understanding that he is in public life and what that means.’
Yet again, Kate and Wills are serving up some top parenting advice.