The parents call their little one, Prince George, "our little grape" and "PG Tips" or just "Tips" - a brand of British tea.
Wills calls his Grandma, The Queen, "Gary" - apparently because he couldn't say granny as a tot!
We know George calls her "Gan-Gan".
And if the insiders are right, Duchess Meghan as been dubbed "Tungsten" by Prince Charles - after the strong metal.
Express.co.uk reports Prince Harry's nicknames are based on fictional characters.
One affectionate nickname given to the redhead Prince is "Potter", after J.K Rowling's fictional wizard "Harry Potter".
Another nickname given to the Duke of Sussex is "Flash", which is in reference to the fictional army officer Harry Flashman.
The final nickname given to the royal is "Gromit", after the fictional dog who looks after his hapless human friend Wallace.