Youngest of the young heirs to the throne of royal families of the world Princess Estelle of Sweden, just a year and four months, is third in line to the throne after her mother, Crown Princess Victoria.
The eldest son of King Mohammed VI, the 11-year-old Crown Prince Moulay Hassan, is next in line to the throne of Morocco on his father's death.
Following the abdication of her grandmother, Queen Beatrix, and the succession of her father, King Willem-Alexander, to the throne, Catharina-Amalia, Princess of Orange (left), 9, became their heiress apparent in the Netherlands. Next in line are her younger sisters, Princess Alexia, eight, and Princess Ariane, six.
Third in line to the Norwegian throne, Princess Ingrid Alexandra, nine, gets a hug from her grandmother, Queen Sonja. Like the United Kingdom, Norway has abandoned their previous law that would make a boy the heir over his eldest sister.
The daughter of Crown Prince Naruhito, the current heir apparent to the Japanese throne, has two names: her personal name, Aiko, and her imperial title, Toshi, making her full name Aiko, Princess Toshi. However, due to male-favoring laws, Princess Toshi won't follow in her father's footsteps and succeed to the throne: Next in line is Crown Prince Naruhito's brother.
Before there was Will and Kate, there was Frederick and Mary. The Australian commoner met the Danish Crown Prince at a pub in Sydney. The couple now has four children, including Prince Christian, third in line to the throne, pictured here on his first day of school.
The Belgian monarchy may be a young one—their first King was appointed in 1830, but with four young royals today, they've grown in size! Prince Philippe, Duke of Brabant is the heir apparent, and he and his wife have four children. His eldest daughter, Princess Elisabeth (to the left of her father), is third in line to the throne, and upon her accession, will become the nation's first female monarch.
If her parents don't have a son, Infanta Leonor of Spain (right), seven, will one day become Queen of Spain. She and her sister, Sofia, are the daughters of the current heir to the throne, Felipe, Prince of Asturias, and his wife Letizia.