@Meelock actually a duke is a prince that was not the crown prince. Once they grow older, they never stay as a "prince". They take other titles and are known for that title to the public but everybody knows that they have royal blood. The daughters and sons can be princess/prince as a "second generation." That is why we how many dukes and marquise [only a few in our history] were able to take over the throne and the reason why the royal married nobles. They all were relative. incest much. Another reason why in our history many of the royal family were very deformed physically speaking and/or mentally.