Richard, 4th Prince of Sayn-Wittgenstein-Berleburg
Richard, 4th Prince of Sayn- Wittgenstein- Berleburg was Prince of Sayn- Wittgenstein- Berleburg from 1904 to 1918.
Leonilla Bariatinskaya
Leonilla Ivanovna Bariatinskaya, Princess of Sayn- Wittgenstein- Sayn( 9 May 1816 – 1 February 1918), was a Russian aristocrat who married Ludwig, Prince of Sayn- Wittgenstein- Sayn.
She was the subject of a number of portraits by Franz Xaver Winterhalter.
Richard, 6th Prince of Sayn-Wittgenstein-Berleburg
Richard, 6th Prince of Sayn-Wittgenstein-Berleburg (Richard Casimir Karl August Robert Konstantin; 29 October 1934 – 13 March 2017) was the head of the House of Sayn-Wittgenstein-Berleburg and husband of Princess Benedikte of Denmark.
John George I, Duke of Saxe-Eisenach
Johann Georg I, Duke of Saxe-Eisenach (Weimar, 12 July 1634 – hunting accident, Eckhartshausen, Marksuhl, 19 September 1686).
He was the fifth but third surviving son of Wilhelm, Duke of Saxe-Weimar and Eleonore Dorothea of Anhalt-Dessau.
After the death of his father (1662), his older brother Johann Ernst II inherited Weimar, and his second brother Adolf Wilhelm received Eisenach.
Johann Georg received an income from the new duchy of Saxe-Eisenach and took his residence in the small town of Marksuhl.
In 1668 his brother Adolf Wilhelm died.
His fifth and only surviving son, Wilhelm August, was born eight days after his father's death and became duke from the moment of his birth; Johann George became the regent of the duchy and also the guardian of the new duke.
Wilhelm August died in 1671 at only two years of age, and Johann Georg inherited the duchy.
The next year (1672) the death without heirs of the Duke Frederick Wilhelm III of Saxe-Altenburg forced a new treaty of division of the family lands between Johann Georg, his surviving brothers and his cousin.
Johann Georg was confirmed in his possession of Eisenach and took some towns, and his younger brother, Bernhard, inherited Jena.
Johann Georg thus became the founder of the most recent line of the dukes of Saxe-Eisenach, who became extinct in 1741.
He was ruler in 1685 when Johann Sebastian Bach was born in the duchy.
Bernhart, Prince of Sayn-Wittgenstein-Hohenstein
Bernhart Otto Peter, 6th Prince of Sayn- Wittgenstein- Hohenstein( born 15 November 1962) is a German businessman and the current head of the Princely House of Sayn- Wittgenstein- Hohenstein.
Gustav, 7th Prince of Sayn-Wittgenstein-Berleburg
Gustav, 7th Prince of Sayn- Wittgenstein- Berleburg( Gustav Frederik Philip Richard; born 12 January 1969), is the eldest child and only son of Princess Benedikte of Denmark and Richard, 6th Prince of Sayn- Wittgenstein- Berleburg.
Johannetta of Sayn-Wittgenstein (1561–1622)
Johanetta of Sayn-Wittgenstein (15 February 1561 – 13 April 1622) was a daughter of Count Louis I of Sayn-Wittgenstein and his first wife, Anna of Solms-Braunfels, who was a relative of Amalia of Solms-Braunfels.
Gustav Albrecht, 5th Prince of Sayn-Wittgenstein-Berleburg
Gustav Albrecht Alfred Franz Friedrich Otto Emil Ernst, 5th Prince of Sayn- Wittgenstein- Berleburg, 28 February 1907 – 1944( declared legally dead 29 November 1969) was Prince and head of the House of Sayn- Wittgenstein.
He was the son of Richard, 4th Prince of Sayn- Wittgenstein- Berleburg.
Louise Juliane of Erbach
Countess Louise Juliane of Erbach( 1603 at Fürstenau Castle near Michelstadt – 28 September 1670 in Friedewald) was a German regent; Countess of Sayn- Wittgenstein- Sayn by marriage to Ernest of Sayn- Wittgenstein- Sayn, she acted temporarily as regent of Sayn- Wittgenstein- Sayn.
She is remembered as the title character of the novel" Die Gräfin von Sayn The Countess of Sayn") by Karl Ramseger- Mühle.
Johannetta of Sayn-Wittgenstein (1632–1701)
Johannetta of Sayn-Wittgenstein (27 August 1632 – 28 September 1701), was Sovereign Countess of Sayn-Wittgenstein-Sayn-Altenkirchen from 1648 to 1701.
She was also Landgravine of Hesse-Braubach by marriage to John, Landgrave of Hesse-Braubach, and Duchess of Saxe-Marksuhl (later Saxe-Eisenach) by marriage to John George I, Duke of Saxe-Eisenach.

Question: Who is the mother-in-law of Johannetta Of Sayn-Wittgenstein (1632–1701)?
Answer: Eleonore Dorothea of Anhalt-Dessau