All members of the Royal Family are expected to bow and curtsy to the Queen at public outings.
Despite children not being required to strictly follow all the rules of the royal protocol, they still have to pay their respects to their great-grandmother.
This means that even little Prince George, 5, and Princess Charlotte, 3, will have to learn how to curtsy at quite a young age.
Historian Marlene Eilers Koenig believes that Prince George, who turned five last Sunday, may have started doing it already.
According to the tradition, she explained, royal children start bowing and curtsying when they turn five.
She told Hello!: “Certainly by age five.
“The only person they will curtsy or bow to is the sovereign.
“A royal highness does not curtsy to another royal highness.
“Yes, there are articles that state this, but it is not true.”
According to Ms Eilers Koenig, royals have to curtsy and bow only to the sovereign, never to another royal highness.
She continued: “Curtsying and bowing is etiquette, nothing to do with precedence.
“You bow or curtsy the first time you see the sovereign and then again when you leave.
“At Christmas at church, we saw the Cambridges and Prince Harry and Meghan curtsy and bow when the Queen arrived and left.
“Other royals including Charles did not because they had come from Sandringham and had already seen the Queen.”
Meghan Markle had to learn how to properly pay her respects to the monarch ahead of her wedding with Prince Harry.
She was first seen performing a perfect curtsy to the Queen in Sandringham last year, when the former actress joined the royals for the Christmas Day service.
Meanwhile, little Princess Charlotte seems very eager to start following this royal rule and has already been seen practising in public.
Last summer, during the Cambridges’s royal tour of Poland, she gave a mini curtsy to the diplomats who had gathered to bid them farewell.