The House of Wettin was a dynasty of German counts, dukes, prince-electors (Kurfürsten) and kings that ruled in what is known today as the German states of Saxony and Thuringia for more than 800 years.  Members of the Wettin family were also kings of Poland, as well as forming the ruling houses of Great Britain, Portugal, Bulgaria, Poland, Saxony, and Belgium.  Today only the British and Belgian lines still rule their countries, but the last Tsar of Bulgaria, Simeon II, was Prime Minister of Bulgaria between 2001 and 2005.  Simeon Saxe-Coburg-Gotha is the only ex-king who has ever returned to his country as an elected leader.

Origins: Wettins of Saxony 
The oldest known member of the House of Wettin was Thiedericus (died 982). Around 1000, as part of the German conquest of Slavic territory, the family got Wettin Castle and changed their name.  It was usual for noblemen to change their name to the name of their territory. Wettin Castle is located in Wettin, Saxony-Anhalt in the Hosgau on the Saale River.

Branches of the House of Wettin 
The House split into two main branches, the Ernestine and the Albertine.  The descendants of Ernest often subdivided their land and ended up with a lot of small duchies, but one (Saxe-Coburg and Gotha) became very important.  Ernest's younger brother was Albert.  His descendants became Electors of Saxony, and in 1806, Kings of Saxony

The House of Saxe-Coburg and Gotha 

Descendants of the Dukes of Saxe-Coburg and Gotha have become:
 kings of Belgium (from 1831) and 
 Bulgaria (1908 - 1946)
and also husbands of the queens of 
 Portugal (Ferdinand II of Portugal) and 
 the United Kingdom (Prince Albert, husband of Queen Victoria).

The wife of the Emperor of Mexico (Carlota of Mexico) was also a member of the house of Saxe-Coburg and Gotha. As such, the British, Portuguese, and for a time, Mexican, thrones became a possession of persons who belonged to the House of Wettin.  

During World War I the British Royal Family changed the name as well as their personal surnames  to Windsor by an Order-in-Council of King George V. The Kings of Belgiums now do not use the Saxe-Coburg and Gotha name, but have never officially changed it.

List of branches of the House of Wettin 
 Margraves of Meissen
 Dukes of Saxony, Landgraves of Thuringia
 Electors of Saxony
 Dukes of Saxe-Coburg
 Dukes of Saxe-Altenburg (first line of Altenburg)
 Dukes of Saxe-Weimar
 Dukes of Saxe-Eisenach
 Dukes of Saxe-Gotha
 Dukes of Saxe-Gotha and Altenburg (second line of Altenburg)
 Dukes of Saxe-Meiningen
 Dukes of Saxe-Hildburghausen, then Dukes of Saxe-Altenburg (third line of Altenburg)
 Dukes of Saxe-Coburg (Gotha later added)
 Kings and Queen of the United Kingdom (House of Windsor)
 Princes of Saxe-Coburg-Kohary
 Kings of Portugal (Saxe-Coburg-Braganza, last reigning Royal House of Portugal)
 Kings of Bulgaria (sometimes had been known as "Kohary" and as "Sakskoburggotski")
 Kings of Belgium
 Dukes of "Saxe-Dresden"
 Electors of Saxony
 Kings of Saxony, currently Prinz/ Prinzessin von Sachsen
 Saxe-Zeitz
 Saxe-Merseburg
 Saxe-Weissenfels
 Dukes of Saxony, Landgraves of Thuringia, Dukes of Luxembourg
 Saxe-Landsberg
 Saxe-Lauenberg

Related pages
 Rulers of Saxony, a list containing many Wettins
 Wettin, Saxony-Anhalt, the city from which the Wettin dynasty originated

References

Other websites 
 The House of Wettin 
 Genealogy of the Wettin dynasty from Genealogy.eu
 Genealogical tables of the Saxony families  from An Online Gotha 

 
 
Holy Roman Empire