Question: Who is the paternal grandfather of Princess Tatiana Of Sayn-Wittgenstein-Berleburg?

Knowledge 1: Princess Tatiana of Sayn-Wittgenstein-Berleburg
Princess Tatiana of Sayn-Wittgenstein-Berleburg (Tatiana Louise Ursula Therese Elsa; born 31 July 1940) is the fourth child and second daughter of Gustav Albrecht, 5th Prince of Sayn-Wittgenstein-Berleburg, and his wife, Margareta Fouché d'Otrante, and younger sister of Prince Richard of Sayn-Wittgenstein-Berleburg, the husband of Princess Benedikte of Denmark.Tatjana is the former wife of the late Moritz, Landgrave of Hesse, from 1980 head of the House of Hesse.Their marriage took place in the summer of 1964 in Gießen.They divorced in 1974. [SEP] Knowledge 2: 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.
Knowledge 1: Princess Tatiana of Sayn-Wittgenstein-Berleburg
Princess Tatiana of Sayn-Wittgenstein-Berleburg (Tatiana Louise Ursula Therese Elsa; born 31 July 1940) is the fourth child and second daughter of Gustav Albrecht, 5th Prince of Sayn-Wittgenstein-Berleburg, and his wife, Margareta Fouché d'Otrante, and younger sister of Prince Richard of Sayn-Wittgenstein-Berleburg, the husband of Princess Benedikte of Denmark.Tatjana is the former wife of the late Moritz, Landgrave of Hesse, from 1980 head of the House of Hesse.Their marriage took place in the summer of 1964 in Gießen.They divorced in 1974. [SEP] Knowledge 2: 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.
Knowledge 1: Princess Tatiana of Sayn-Wittgenstein-Berleburg
Princess Tatiana of Sayn-Wittgenstein-Berleburg (Tatiana Louise Ursula Therese Elsa; born 31 July 1940) is the fourth child and second daughter of Gustav Albrecht, 5th Prince of Sayn-Wittgenstein-Berleburg, and his wife, Margareta Fouché d'Otrante, and younger sister of Prince Richard of Sayn-Wittgenstein-Berleburg, the husband of Princess Benedikte of Denmark.Tatjana is the former wife of the late Moritz, Landgrave of Hesse, from 1980 head of the House of Hesse.Their marriage took place in the summer of 1964 in Gießen.They divorced in 1974. [SEP] Knowledge 2: Margareta Fouché
Margareta Fouché d' Otrante, Princess of Sayn- Wittgenstein- Berleburg( 28 March 1909 – 25 August 2005) was the wife of Gustav Albrecht, 5th Prince of Sayn- Wittgenstein- Berleburg, and mother of Richard, 6th Prince of Sayn- Wittgenstein- Berleburg, who married Princess Benedikte of Denmark.The daughter of Charles Louis Fouché, 6th Duke of Otranto( a descendant of Napoleonic statesman Joseph Fouché) and his first wife, Countess Hedvig Ingeborg Madeleine Douglas( a descendant of Louis I, Grand Duke of Baden), she was born Margareta Fouché d' Otrante in Elghammar, Sweden.Her husband," Rittmeister" Gustav Albrecht, was the head of the mediatized princely house of Sayn- Wittgenstein- Berleburg.He went missing in action in 1944, during World War II, and was declared legally dead in 1969.From 1944 to 1955, after her husband was reported missing, Margareta, as Princess Dowager, became the guardian for her son, Prince Richard, and managed her late husband's properties.The family went into exile in her native Sweden.Prince Richard later married Princess Benedikte of Denmark.

Answer: Richard, 4th Prince of Sayn-Wittgenstein-Berleburg