Royal Heirs Around the World

From left, Prince Felipe of Spain, Princess Leonor of Spain, Princess Sofia of Spain and Princess Letizia of Spain meet Pope Benedict XVI during World Youth Day 2011 celebrations at Zarzuela Palace, Aug. 19, 2011 in Madrid, Spain. Prince Felipe is the only son of the current King of Spain Juan Carlos. He is the next heir to the throne, followed by his daughters, Leonor and Sofia. (Fotonoticias/Getty Images)