It’s fair to say that Prince William is a man of many titles. He’s known, for example, as not only His Royal Highness The Duke of Cambridge but also both His Royal Highness The Earl of Strathearn and Baron Carrickfergus. And of course, one day, he’ll also be king. According to his wife, Kate, though, William’s eldest son isn’t nearly so formal when addressing his father. Instead, he has a rather sweet nickname for the prince.