Nicholas's mother, his father's first cousin's daughter, was a daughter of Duke Konstantin Peter of Oldenburg (1812–1881) and Princess Therese of Nassau (1815–1871). His maternal grandfather was a son of Duke George of Oldenburg and Grand Duchess Catherine Pavlovna of Russia, daughter of Paul I of Russia and Maria Fedorovna of Württemberg. (Catherine was later remarried to William I of Württemberg.) His maternal grandmother was a daughter of Wilhelm, Duke of Nassau (1792–1839) and Princess Luise of Saxe-Hildburghausen. The Duke of Nassau was a son of Friedrich Wilhelm, Duke of Nassau (1768–1816) and Burgravine Louise Isabelle of Kirchberg. His paternal grandparents were Duke Karl Christian of Nassau-Weilburg (1735–1788) and Carolina of Orange-Nassau. Carolina was a daughter of William IV of Orange and Anne, Princess Royal and Princess of Orange. Anne was the eldest daughter of George II of Great Britain and Caroline of Ansbach.