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.
George II, Prince of Anhalt-Dessau
George II, Prince of Anhalt- Dessau( 1454 – 25 April 1509) was a German prince of the House of Ascania and ruler of the principality of Anhalt- Dessau.
He was the fourth son of George I, Prince of Anhalt- Dessau, as second- born child of his fourth wife Anna, daughter of Albert VIII, Count of Lindau- Ruppin.
George I, Prince of Anhalt-Dessau
George I, Prince of Anhalt- Dessau( – 21 September 1474), was a German prince of the House of Ascania and ruler of the principality of Anhalt- Dessau.
He was the second son of Sigismund I, Prince of Anhalt- Dessau, by his wife Judith, daughter of Gebhard XI, Count of Querfurt.
Waldemar IV, Prince of Anhalt-Dessau
Waldemar IV, Prince of Anhalt- Dessau( died aft. 22 July 1417) was a German prince of the House of Ascania and ruler of the principality of Anhalt- Dessau.
He was the eldest son of Sigismund I, Prince of Anhalt- Dessau, by his wife Judith, daughter of Gebhard XI, Count of Querfurt.
Countess Henriette Catherine of Nassau
Henriette Catherine of Nassau (10 February 1637 – 3 November 1708) was princess consort of Anhalt-Dessau by marriage to John George II, Prince of Anhalt-Dessau, and regent of Anhalt-Dessau from 1693 to 1698 during the minority (and then the absence) of her son Leopold I, Prince of Anhalt-Dessau.
Rudolph IV, Prince of Anhalt-Dessau
Rudolph IV, Prince of Anhalt- Dessau( died 7 September 1510) was a German prince of the House of Ascania and ruler of the principality of Anhalt- Dessau.
He was the fifth son of George I, Prince of Anhalt- Dessau, as the fourth- born child of his fourth wife Anna, daughter of Albert VIII, Count of Lindau- Ruppin.
William Gustav of Anhalt-Dessau
William Gustav of Anhalt- Dessau( 20 June 1699 – 16 December 1737) was a German prince of the House of Ascania and heir to the principality of Anhalt- Dessau.
He was born in Dessau, the eldest son of Leopold I, Prince of Anhalt- Dessau, by his morganatic wife Anna Louise Föhse.
Sigismund II, Prince of Anhalt-Dessau
Sigismund II, Prince of Anhalt- Dessau( died aft. 22 May 1452) was a German prince of the House of Ascania and ruler of the principality of Anhalt- Dessau.
He was the fourth son of Sigismund I, Prince of Anhalt- Dessau, by his wife Judith, daughter of Gebhard XI, Count of Querfurt.
Albert V, Prince of Anhalt-Dessau
Albert V, Prince of Anhalt- Dessau( died ca. 1469) was a German prince of the House of Ascania and ruler of the principality of Anhalt- Dessau.
He was the fifth son of Sigismund I, Prince of Anhalt- Dessau, by his wife Judith, daughter of Gebhard XI, Count of Querfurt.
Princess Agnes of Anhalt-Dessau
Princess Agnes of Anhalt-Dessau (Frederica Amalia Agnes; 24 June 1824 – 23 October 1897) was the eldest daughter of Leopold IV, Duke of Anhalt by his wife Princess Frederica of Prussia.
She was a member of the House of Ascania, and by her marriage to Ernst I, Duke of Saxe-Altenburg, Duchess consort of Saxe-Altenburg.

Question: Who is the father-in-law of Princess Agnes Of Anhalt-Dessau?