House of Lorraine

The House of Lorraine was a family from the Duchy of Lorraine in modern day France. The family ruled the small duchy of Lorraine. They later ruled the Grand Duchy of Tuscany. Empress Maria Theresa of Austria was married to a Duke of Lorraine. Thus joined the house of Lorraine with the House of Habsburg. The House of Habsburg was very powerful. 
The House of Lorraine, the main and now only remaining line known as Habsburg-Lorraine, is one of the most important and was one of the longest-reigning royal houses in the history of Europe. Currently the house is headed by Karl Habsburg-Lothringen, the titular Emperor of Austria, King of Hungary, Bohemia, Galicia and Lodomeria, Croatia, Illyria, as well as the titular King of Jerusalem.