Prince Moritz of Saxe-Altenburg
Prince Moritz Franz Friedrich Constantin Alexander Heinrich August Carl Albrecht of Saxe- Altenburg( 24 October 1829 in Eisenberg – 13 May 1907 in Arco, Italy), was a member of the ducal house of Saxe- Altenburg.
He was the father of Ernst II, Duke of Saxe- Altenburg.
Princess Antoinette of Saxe-Altenburg
Princess Antoinette of Saxe- Altenburg( 17 April 1838 – 13 October 1908) was a princess of Saxe- Altenburg by birth and Duchess of Anhalt by marriage.
Princess Elisabeth Sophie of Saxe-Altenburg
Elisabeth Sophie of Saxe- Altenburg( 10 October 1619 – 20 December 1680), was a princess of Saxe- Altenburg and, by marriage, duchess of Saxe- Gotha.
She was born in Halle, the only daughter of Johann Philipp, Duke of Saxe- Altenburg, and his wife, Elisabeth of Brunswick- Wolfenbüttel.
Princess Marie Anne of Saxe-Altenburg
Princess Marie Anne of Saxe-Altenburg (14 March 1864 – 3 May 1918) was the consort of Georg, Prince of Schaumburg-Lippe.
As the eldest daughter of Prince Moritz of Saxe-Altenburg and his wife Princess Augusta of Saxe-Meiningen, and a sister of Ernest II, Duke of Saxe-Altenburg, Marie Anne was a member of the Ducal House of Saxe-Altenburg.
Princess Charlotte of Saxe-Altenburg
Princess Charlotte Agnes of Saxe- Altenburg( 4 March 189916 February 1989) was the eldest child of Ernst II, the last reigning duke of Saxe- Altenburg.
Prince Eduard of Saxe-Altenburg
Eduard Karl Wilhelm Christian of Saxe- Altenburg( Hildburghausen, 3 July 1804 – Munich, 16 May 1852), was a German prince of the ducal house of Saxe- Hildburghausen( of Saxe- Altenburg from 1826).
Princess Marie of Hanover
Princess Marie of Hanover (2 December 1849 – 4 June 1904) was the younger daughter of King George V of Hanover and of his wife, Princess Marie of Saxe-Altenburg.
Ernst I, Duke of Saxe-Altenburg
Ernst I, Duke of Saxe- Altenburg( German: Ernst I. Friedrich Paul Georg Nikolaus von Sachsen- Altenburg)( 16 September 1826 in Hildburghausen – 7 February 1908 in Altenburg), was a duke of Saxe- Altenburg.
He was the first son of Georg, Duke of Saxe- Altenburg and Marie Luise of Mecklenburg- Schwerin.
In 1853 he succeeded his father as Duke of Saxe- Altenburg.
He was of a retiring disposition and he took little active part in running the country.
After a reign that lasted fifty five years, he died without a living direct male heir; because of this, he was succeeded by his nephew, Ernst.
Georg Moritz, Hereditary Prince of Saxe-Altenburg
George Moritz, Hereditary Prince of Saxe- Altenburg(" William George Moritz Ernest Albert Frederick Charles Constantine Edward Maximilian"; 13 May 1900 – 13 February 1991), was the last head of the ducal house of Saxe- Altenburg and nominal Duke of Saxe- Altenburg.
He devoted much of his life to promote anthroposophy.
Princess Augusta of Saxe-Meiningen
Princess Augusta Louise Adelaide Caroline Ida of Saxe-Meiningen (6 August 1843 – 11 November 1919) was the daughter of Bernhard II, Duke of Saxe-Meiningen and his wife Princess Marie Frederica of Hesse-Kassel.
She was the mother of Ernst II, Duke of Saxe-Altenburg.

Question: Who is the maternal grandfather of Princess Marie Anne Of Saxe-Altenburg?
Answer: Bernhard II, Duke of Saxe-Meiningen