Really.. I did not know that. Please explain....
HRH Friedrich Wilhelm Ludwig Prince of Prussia
(later FRIEDRICH WILHELM IV, King of Prussia (Berlin 15 Oct 1795-Sans Souci, Potsdam 2 Jan 1861) , brother of Friederike Luise Charlotte Wilhelmine, took the name Alexandra Feodorovna on her Orthodox baptism (Berlin 13 Jul 1798-St.Petersburg 1 Nov 1860); m.St.Petersburg 13 Jul 1817 Emperor Nicholas I of Russia (Gatschina 6 Jul 1796-St.Petersburg 2 Mar 1855) )
with Katarina Countess Tiesenhausen ( Father Ferdinand Count Tiesenhausen and mother HSH Princessa Elizaveta Golenischeva -Kutuzova, daugther of fieldmarshal HSH Prince Michail Kutuzov-Smolenski )
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General Felix Nikolaevich Elston 1820-1877 , nobleman of Grand Duchy Baden 1836 (1839?), count Sumarakov-Elston 1856 , wife Elena Sergeevich Sumarokova (father General Count Sergei Sumarokov, mother Marchesa Alexandra Maruzzi )
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General Count Felix Felixovich Sumarokov- Elston 1856-1928, Prince Yussupov, wife Princess Zinaida Nikolaevich Yussupov ( father last origin prince Yussupov, Nikolai , mother Countess Tatiana Alexandrovich Ribeaupierre)
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Felix Felixovich Prince Yussupov, Count Sumarokov- Elston, 1887-1967, wife HH Irina Princess of Russia 1895-1970
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Irina Felixovich Princess Yussupova, Countess Sumarokova- Elston 1915 - 1983, husband Count Nikolai Scheremetiev 1904 - 1979
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Xenia Nikolaevna Sheremetieva, Countess b. 1942