How long has Princess Margaretha of Liechtenstein's brother reigned as Grand Duke?
Princess Margaretha of Liechtenstein:  As the sister of Grand Duke Henri of Luxembourg and the sister-in-law of Prince Hans-Adam II of Liechtenstein, she is a princess of two current realms and a member of the Luxembourg and Liechtenstein reigning dynasties. Henri, Grand Duke of Luxembourg: Henri (Luxembourgish: "Henri Albert Gabriel Félix Marie Guillaume" , ] ; born 16 April 1955) is the current Grand Duke of Luxembourg, reigning since 7 October 2000.
since 7 October 2000.