This is when Prince George, Princess Charlotte and Prince Louis will start bowing to the Queen

There are a lot of rules when it comes to correctly greeting your family, friends and peers when you're a part of the royal family.

Who gets in the car first? Who bows to who? And when will Prince William and Kate Middleton's three children have to start bowing to the Queen?

Royal historian, Marlene Eilers Koenig, believes that the little royals will start bowing to their great-grandmother quite soon - if they haven't already.

'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,' she explained to Hello! magazine.

'Yes, there are articles that state this, but it is not true.'

She continued: 'Curtseying 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.'

George turns is eight years old, and Princess Charlotte is six, meaning that if the royal historian is right they will already be bowing to the Queen - but at the moment, little Prince Louis may have a little longer before he has to follow the royal protocol as he only recently turned four.

So, now you know!