Complex sentence: Officially the last Russian tsaritsa was Eudoxia Lopukhina, Peter the Great's 1st wife, ans the last Russian Empress was Alexandra Fyodorovna (Alix of Hesse), the wife of Nicholas II of Russia.
Split into simpler sentences: Officially the last Russian tsaritsa was Eudoxia Lopukhina, Peter the Great's 1st wife. Last Russian Empress was Alexandra Fyodorovna (Alix of Hesse) who was married to Nicholas II of Russia.