Complex sentence: Mechthildis's mother, Archduchess Maria Theresa of Austria, Princess of Tuscany was a granddaughter of Leopold II, the last reigning Grand Duke of Tuscany, on her mother line she was a grand daughter of King Ferdinand II of the Two Sicilies.
Split into simpler sentences: Mechthildis's mother, Archduchess Maria Theresa of Austria, Princess of Tuscany was a granddaughter of Leopold II, the last reigning Grand Duke of Tuscany. On her mother line, she was a grand daughter of King Ferdinand II of the Two Sicilies.