Question: How long has Princess Margaretha of Liechtenstein's brother reigned as Grand Duke?

Related documents: [0]  [DOC] Henri (Luxembourgish: "Henri Albert Gabriel Félix Marie Guillaume" , ] ; born 16 April 1955) is the current Grand Duke of Luxembourg, reigning since 7 October 2000. He is the eldest son of Grand Duke Jean and Princess Joséphine-Charlotte of Belgium, and a first cousin of Philippe, the current king of Belgium. [END] 
[1]  [DOC] Princess Margaretha of Liechtenstein (born "Princess Margaretha of Luxembourg" on 15 May 1957) is the fourth child and second daughter of Grand Duke Jean of Luxembourg and Princess Joséphine Charlotte of Belgium. 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. The Princess holds similar precedence in both monarchies, as sister and sister-in-law of the Sovereign. [END]  
Answer: since 7 October 2000.
since 7 October 2000.