Prince Friedrich Sigismund of Prussia (1891–1927)
Prince Joachim Viktor Wilhelm Leopold Friedrich Sigismund of Prussia( 17 December 1891 – 6 July 1927) was a German World
War I fighter pilot and member of the House of Hohenzollern.
He was the son of Prince Friedrich Leopold of Prussia and Princess Louise Sophie of Schleswig- Holstein- Sonderburg- Augustenburg, married in 1916.
Joachim Ernest, Duke of Schleswig-Holstein-Sonderburg-Plön
Joachim Ernest of Schleswig-Holstein- Sonderburg- Plön( 29 August 1595 – October 5, 1671), also" Joachim Ernest of Schleswig- Holstein- Plön", was the first Duke of Schleswig- Holstein- Sonderburg- Plön, which emerged from a division of the Duchy of Schleswig- Holstein- Sonderburg.
Princess Adelheid of Hohenlohe-Langenburg
Princess Adelheid of Hohenlohe-Langenburg (20 July 1835 – 25 January 1900) was Duchess of Schleswig-Holstein, a niece of Queen Victoria of the United Kingdom, a cousin of King Edward VII, and the mother-in-law of Emperor Wilhelm II of Germany.
She is the direct most recent common matrilineal ancestress (through women only) of Carl XVI Gustaf of Sweden and Felipe VI of Spain.
Princess Louise Sophie of Schleswig-Holstein-Sonderburg-Augustenburg
Princess Louise Sophie of Schleswig-Holstein-Sonderburg-Augustenburg
(German: Feodora Luise Sophie Adelheid Henriette Amalie; 8 April 1866 - 28 April 1952) was a daughter of Frederick VIII, Duke of Schleswig-Holstein and Princess Adelheid of Hohenlohe-Langenburg.
Friedrich, Duke of Schleswig-Holstein-Sonderburg-Glücksburg
Friedrich of Schleswig- Holstein- Sonderburg- Glücksburg( 23 October 1814 in Schleswig, Duchy of Schleswig – 27 November 1885 in Luisenlund, Schleswig- Holstein, Prussia) was the third Duke of Schleswig- Holstein- Sonderburg- Glücksburg.
Friedrich was the second- eldest son of Friedrich Wilhelm, Duke of Schleswig- Holstein- Sonderburg- Glücksburg and Princess Louise Caroline of Hesse- Kassel and an elder brother of Christian IX of Denmark.
Friedrich inherited the title of Duke of Schleswig- Holstein- Sonderburg- Glücksburg upon his childless brother Karl's death on 14 October 1878.
Princess Victoria Margaret of Prussia
Princess Victoria Margaret Elizabeth Marie Ulrike of Prussia (17 April 1890 – 9 September 1923) was a member of the House of Hohenzollern.
She was the eldest daughter of Prince Friedrich Leopold of Prussia and his wife Princess Louise Sophie of Schleswig-Holstein-Sonderburg-Augustenburg.
She married Prince Heinrich XXXIII Reuss of Köstritz and had two children.
Friedrich Ferdinand, Duke of Schleswig-Holstein
Friedrich Ferdinand of Schleswig- Holstein- Sonderburg- Glücksburg( 12 October 1855 – 21 January 1934) was the fourth Duke of Schleswig- Holstein- Sonderburg- Glücksburg and became Duke of Schleswig- Holstein in 1931.
Prince Frederick of Schleswig-Holstein-Sonderburg-Augustenburg
Prince Frederick Emil August of Schleswig-Holstein- Sonderburg- Augustenburg( Kiel, 23 August 1800 – Bayreuth, Germany, 2 July 1865), usually simply known by just his first name, Frederick," Prince of Noer", was a prince of the House of Schleswig- Holstein- Sonderburg- Augustenburg and a cadet- line descendant of the Danish royal house.
He was the second and youngest son of Louise Auguste of Denmark and Frederik Christian II, Duke of Schleswig- Holstein- Sonderburg- Augustenburg.
As such, he was close to succeed in the Danish throne.
He was the brother- in- law of King Christian VIII and nephew of King Frederik VI.
His elder brother, Christian August II, succeeded in 1814 as the Duke of Schleswig- Holstein- Sonderburg- Augustenburg.
After his second, morganatic union, he renounced the rights of succession to House of Augustenburg.
He was created Prince of Noer or Nør by Emperor Franz Joseph of Austria afterwards.
Prince Frederick died 1865 at Bayreuth.
Princess Alexandra Victoria of Schleswig-Holstein-Sonderburg-Glücksburg
Princess Alexandra Victoria of Schleswig-Holstein- Sonderburg- Glücksburg( 21 April 1887 – 15 April 1957) was a daughter of Friedrich Ferdinand, Duke of Schleswig- Holstein and his wife Princess Karoline Mathilde of Schleswig- Holstein- Sonderburg- Augustenburg.
Karl, Duke of Schleswig-Holstein-Sonderburg-Glücksburg
Karl of Schleswig -Holstein- Sonderburg- Glücksburg( 30 September 1813 at Gottorp in Schleswig, Duchy of Schleswig – 24 October 1878 at Luisenlund, Glücksburg, in Schleswig- Holstein, Prussia) was the second Duke of Schleswig- Holstein- Sonderburg- Glücksburg.
Karl was the eldest son of Friedrich Wilhelm, Duke of Schleswig- Holstein- Sonderburg- Glücksburg and Princess Louise Caroline of Hesse- Kassel and an elder brother of Christian IX of Denmark.
Karl became Duke of Schleswig- Holstein- Sonderburg- Glücksburg upon his father's death on 27 February 1831.

Question: What is the date of death of Princess Louise Sophie Of Schleswig-Holstein-Sonderburg-Augustenburg's mother?
Answer: 25 January 1900