UNITED KINGDOM AND 15 COMMONWEALTHS: Queen Elizabeth II has reigned since 1952, when her father died. She has four children and eight grandchildren. The heir apparent is her son Charles, Prince of Wales. Queen Elizabeth and Prince Philip are seen at the House of Lords during the State Opening of Parliament in Westminster in London on May 25. Leon Neal/AP
KINGDOM of BELGIUM: Belgium established itself as a constitutional monarchy in 1831, after it gained independence from the Netherlands. The king (currently King Albert II) is also the head of state and, as in England, appoints the prime minister who has received majority support in parliament. The Belgian royal family arrives for a gala concert at the Laeken Royal Palace in Brussels in July 2. Jan Van de Vel/Reuters
KINGDOM OF SPAIN: King Juan Carlos I has been king since 1975. His grandfather, King Alfonso XIII fled the country in 1931 with establishment of a republic. General Francisco Franco appointed himself head of state in 1936, but passed a law of succession that a new king would be named. Juan Carlos pushed for the democratization of Spain and helped restore democratic rule after an attempted military coup in 1981. Prince Felipe (r.) and Princess Letizia smile during a visit to the Infanta Leonor nursery in Piedras Blancas, Spain, on May 20. Eloy Alonso/Reuters
KINGDOM of DENMARK: The country established itself as a constitutional monarchy in 1849. The current leader, Queen Margrethe II, is largely ceremonial. The Danish royal family is seen here on April 16 on the balcony of Amalienborg Palace in Copenhagen, Denmark. Tariq Mikkel Khan/AP
KINGDOM OF NORWAY: Ruled today by King Harald V, who succeeded his father in 1991. Will be succeeded by his son, Crown Prince Haakon. The first king of Norway, King Harald I united Norway in the beginning of the 9th century. The Royal Motto: “Everything for Norway.” King Harald (l.) and Queen Sonja (3rd l.) are seen at the Royal Palace in Oslo, Norway, on June 1. Lise Aserud/Reuters
GRAND DUCH OF LUXEMBOURG: Led by Grand Duke Henri, it became an independent state after signing the Treaty of London in 1839. Henri is the world’s only Grand Duchy (a title ranking below king, but higher than a Duke or Prince). Grand Duke Henri (2nd r.) and Grand Duchess Maria Teresa (r.) arrive at the Swedish Government's dinner in Stockholm, Sweden, on June 18. Bertil Ericson/AP
KINGDOM OF THE NETHERLANDS: The constitutional monarch was established in 1848. Prior to that, the Dutch hereditary monarchy was initiated in 1815 with King William I. Queen Beatrix Wilhemina Armgard, succeeded her mother as queen of the Netherlands in 1980. She will be succeeded by her eldest son, Prince Willem-Alexander. Crown Princess Maxima (l.), Crown Prince Willem-Alexander, and their daughter Catharina-Amalia pose for the media outside a hotel in Stockholm, Sweden, on June 17. Marc Feminia/AP
PRINCIPALITY OF LIECHTENSTEIN: Founded in 1719 as part of the Holy Roman Empire, the current head of state is Prince Hans-Adam II. A new constitution was adopted in 2003 that expanded the monarch’s powers. Princess Sophie (l.) and Erbprinz Alois arrive at the Swedish Parliament's concert at the Royal Concert Hall in Stockholm, Sweden, on June 18. Maja Suslin/AP
PRINCIPALITY OF MONACO: Albert II, the sovereign prince of Monaco, is head of the House of Grimaldi, established in 1297. Monaco became a constitutional monarchy in 1911. Prince Albert II of Monaco speaks with his fiance Charlene Wittstock at the Mare Nostrum XXVII International Swimming Meeting in Monaco, on June 14. Claude Paris/AP
KINGDOM OF SWEDEN: At the age of 27, King Carl XVI Gustav became king. Swedish kings date back to 980. He succeeded his grandfather (his father died in 1947, a year after the king was born) in 1973. He will be succeeded by his daughter, Crown Princess Victoria. Crown Princess Victoria and her fiance Daniel Westling are seen on stage on June 18 at the Royal Concert Hall in Stockholm, Sweden, ahead of their wedding on June 19. Henrik Montgomery/Reuters
A statement from the Dutch government said the prince's condition was stable, but his life remains at risk.
An avalanche buried and seriously injured the second son of Dutch Queen Beatrix while he skied off the trail Friday in the westernmost corner of Austria and he was rushed to the intensive care unit of an Innsbruck hospital, officials said.