What would the Downton Abbey clan have to say about all these changes in titles? The queen has signed a royal decree that the firstborn child of the Duke and Duchess of Cambridge will have title prince or princess. Previously only the eldest son held the prince title; a firstborn daughter would get the title of lady. The decree comes as the queen has put in motion changes to allow a firstborn daughter to inherit the throne regardless of whether she is followed by a boy. The law is likely to be changed in time for the birth of William and Catherine’s firstborn, expected later this year.