 He was the third but second surviving son of Georg, Duke of Saxe-Altenburg and Duchess Marie Louise of Mecklenburg-Schwerin (daughter of Frederick Louis, Hereditary Grand Duke of Mecklenburg-Schwerin and his first wife Grand Duchess Elena Pavlovna of Russia).In Meiningen on 15 October 1862 Moritz married Princess Augusta of Saxe-Meiningen, daughter of Bernhard II, Duke of Saxe-Meiningen.They had five children