Harry and Meghan's baby boy is not officially a royal, despite being seventh in line to the throne, after George V limited titles within the family during the First World War.
HRH status normally lapses after two royal generations - except for the eldest son of the eldest son of the eldest son of the monarch, which is Prince George.
But the Queen decreed all of William and Kate's children should be HRH - which is why Princess Charlotte is not Lady Charlotte, and Prince Louis is not Lord Louis.
This is why George V's grandchildren the Duke of Gloucester, the Duke of Kent, Prince Michael of Kent and Princess Alexandra are HRH but their children are not.
However, the rules can be changed if the monarch wishes - so Baby Sussex could still officially become a royal.This is why George V's grandchildren the Duke of Gloucester, the Duke of Kent, Prince Michael of Kent and Princess Alexandra are HRH but their children are not.
Additionally, once Prince Charles becomes King, the baby will automatically become HRH because they will then be the grandchild of a reigning sovereign.
Just seven years ago the Queen changed the rules for the benefit of the children of the Duke and Duchess of Cambridge, who had yet to start a family at that time.
She decreed all of their children should be HRH, not just Prince George - which gives Princess Charlotte and Prince Louis their royal titles.