Britain's Prince George doesn't know he is set to be king.
Prince William, 33, and his wife Duchess Catherine, 33, have also not told their two-year-old son that he is a member of the most famous royal family in the world.
During an interview with the BBC that aired on Wednesday (21.01.14), on the eve of his grandmother Queen Elizabeth II's 90th birthday, the father-of-two revealed there will be a "time and a place" in the future to break the news to the little boy, who will turn three in July.
He said: "There will be a time and place to bring George up and understand how he fits in the world."
The Duke of Cambridge - who also has 11-month-old daughter Charlotte - added: "Right now it's just a case of keeping a secure and stable environment and showing him as much love as I can as a father."
Meanwhile, Prince William confessed it is difficult to imagine himself as holding the rank of king, because it would mean his father and the heir apparent to the throne Prince Charles and his grandmother would have "moved on".
Asked if he ponders what type of king he will be, he said: "It occupies a lot of my thinking space as to how on earth you'd develop into something modern in today's world."
But it doesn't keep him awake at night because "it means my family have moved on and I don't want that".