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.
Prince Frederick of Schaumburg-Lippe
Prince Frederick of Schaumburg- Lippe( 30 January 186812 December 1945) was a German prince and head of the Náchod branch of the princely house of Schaumburg- Lippe.
He was a son of Prince William of Schaumburg- Lippe, by his wife Princess Bathildis of Anhalt- Dessau.
Heinrich Donatus, Hereditary Prince of Schaumburg-Lippe
Heinrich Donatus, Hereditary Prince of Schaumburg- Lippe( Ernst- August Alexander Wilhelm Bernhard Krafft Heinrich Donatus; born 13 May 1994) is the son of Alexander, Prince of Schaumburg- Lippe and thus heir to the German Princely house of Schaumburg- Lippe.
Prince Heinrich Donatus of Schaumburg- Lippe was born in Hanover to Alexander, Hereditary Prince of Schaumburg- Lippe( born 1958), and Princess Marie- Louise(" Lilly") of Sayn- Wittgenstein- Berleburg( born 1972), who had married in August 1993.
His mother suffered a nervous breakdown in 1998, and left her husband in 2000 to move with her son from Hanover to Munich.
The couple divorced in 2002.
On the death of his father, Philip- Ernst, Prince of Schaumburg- Lippe, Alexander inherited the title Prince of Schaumburg- Lippe, while his son became Hereditary Prince.
In 2007, the Prince of Schaumburg- Lippe married lawyer Nadja Anna Zsoeks.
Princess Marie- Louise is now married to designer Lambros Milona, with whom she has a daughter, Lana.
Princess Adelheid of Schaumburg-Lippe
Princess Adelheid of Schaumburg-Lippe (9 March 1821 in Bückeburg, Schaumburg-Lippe – 30 July 1899 in Itzehoe, Schleswig-Holstein, Germany) was a member of the House of Schaumburg-Lippe and a Princess of Schaumburg-Lippe by birth.
Through her marriage to Friedrich, Duke of Schleswig-Holstein-Sonderburg-Glücksburg, Adelheid was a sister-in-law of Christian IX of Denmark and Duchess consort of Schleswig-Holstein-Sonderburg-Glücksburg from 14 October 1878 to 27 November 1885.
Georg, Prince of Schaumburg-Lippe
Georg, Prince of Schaumburg- Lippe( 10 October 1846 – 29 April 1911) was a ruler of the small Principality of Schaumburg- Lippe.
Wolrad, Prince of Schaumburg-Lippe
Ernst Wolrad, Prince of Schaumburg- Lippe( 19 April 1887 – 15 June 1962) was a head of the Princely House of Schaumburg- Lippe.
Landgravine Juliane of Hesse-Philippsthal
Juliane of Hesse- Philippsthal( 8 June 1761 – 9 November 1799), was a countess of Schaumburg- Lippe, married in 1780 to Count Philip II, Count of Schaumburg- Lippe.
She served as the regent of Schaumburg- Lippe during the minority of her son from 1787 to 1799.
Frederick Christian, Count of Schaumburg-Lippe
Friedrich Christian, Count of Schaumburg- Lippe( 16 August 1655 – 13 June 1728) was the second ruler of the County of Schaumburg- Lippe.
Adolf I, Prince of Schaumburg-Lippe
Adolf I, Prince of Schaumburg-Lippe (1 August 1817 – 8 May 1893) was a ruler of the Principality of Schaumburg-Lippe.
Adolf II, Prince of Schaumburg-Lippe
Adolf II, Prince of Schaumburg- Lippe( 23 February 1883 – 26 March 1936) was the last ruler of the small Principality of Schaumburg- Lippe.

Question: Who is the mother-in-law of Princess Adelheid Of Schaumburg-Lippe?
Answer: Princess Louise Caroline of Hesse-Kassel