When it comes to British royalty there are only two ways to become a princess. You have to either marry a prince, or be the daughter to one.
So both the leading ladies in Prince William's life are princesses, Kate Middleton who married the prince and Charlotte who was born to her dad.
While her father's children automatically inherited their titles, her children will not.
“Her children will not have titles because the royal titles go down the male line,” Joe Little, managing editor of Majesty, tells PEOPLE.
That means when Prince George has children, they will automatically receive titles the way he and his sister did, even though Charlotte's won't.
But that doesn't mean there aren't exceptions to the rule.