Prince August Leopold of Saxe-Coburg and Gotha
Prince August Leopold of Saxe- Coburg and Gotha( December 6, 1867 – October 11, 1922), known in Brazil as Dom Augusto Leopoldo, was a prince of the Empire of Brazil and of the House of Saxe- Coburg and Gotha- Koháry.
He was the second of four sons born to German Prince Ludwig August of Saxe- Coburg and Gotha and Princess Leopoldina of Brazil.
The second grandson of the Emperor Pedro II, the prince was, for some years between the presumptive heirs to the Imperial Crown of Brazil.
Their descendants would form the Saxe- Coburg and Gotha branch of the Imperial House of Brazil.
Princess Teresa Cristina of Saxe-Coburg and Gotha
Princess Teresa Cristina of Saxe- Coburg and Gotha( 23 August 1902 – 24 January 1990), was a German princess of the House of Saxe- Coburg and Gotha.
Prince Johannes Heinrich of Saxe-Coburg and Gotha
Prince Johannes Heinrich of Saxe- Coburg and Gotha( Johannes Heinrich Friedrich Werner Konrad Rainer Maria; Slovak:" Ján Henrich", Hungarian:" János Henrik"; 28 March 1931, in Innsbruck – 14 April 2010, in Innsbruck) was a prince of the House of Saxe- Coburg and Gotha- Koháry and the last holder of Csábrág and Szitnya, both in modern -day Slovakia, lost to the communist regime of Czechoslovakia.
He was the only son of Prince Rainer of Saxe- Coburg and Gotha by his first wife, Johanna Károlyi de Károly- Patty.
Princess Dorothea of Saxe-Coburg and Gotha
Princess Dorothea Maria Henriette Auguste Louise of Saxe-Coburg and Gotha (30 April 1881 – 21 January 1967) was a princess of Saxe-Coburg and Gotha  by birth and the duchess of Schleswig-Holstein  through her marriage to Ernst Gunther, duke of Schleswig-Holstein.
Dorothea was born in Vienna, Austria, the second child and only daughter of Prince Philipp of Saxe-Coburg and Gotha and Princess Louise of Belgium.
Princess Mathilde of Saxony (born 1936)
Princess Mathilde of Saxony, Duchess of Saxony (17 January 1936 – 18 March 2018) was a Princess of Saxony and member of the House of Wettin by birth and a Princess of Saxe-Coburg and Gotha as consort to Prince Johannes Heinrich of Saxe-Coburg and Gotha.
Mathilde is the fifth and youngest child of Friedrich Christian, Margrave of Meissen and his wife, Princess Elisabeth Helene of Thurn and Taxis, and a younger sister of Maria Emanuel, Margrave of Meissen, the late head of the Royal House of Saxony and senior claimant to the defunct throne of the Kingdom of Saxony.
Hubertus, Hereditary Prince of Saxe-Coburg and Gotha
Hubertus Michael, Hereditary Prince of Saxe- Coburg and Gotha, Duke of Saxony( born 16 September 1975) is the heir- apparent of the head of the family which ruled the Duchy of Saxe- Coburg and Gotha until 1918.
Prince Johannes of Saxe-Coburg and Gotha
Johannes Albert Leopold Frederick Christian, Prince of Saxe-Coburg-Koháry, in Slovak: "Ján ...", in Hungarian: "János ...", in German: "Johannes Albert Leopold Friedrich Christian Erbprinz von Sachsen-Coburg-Kohary" (17 November 1969, in Innsbruck – 21 August 1987, in Ortler) was a German royal (prince from the House of Saxe-Coburg and Gotha-Koháry) and presumed heir of his maternal uncle, the childless Maria Emanuel, Margrave of Meissen, Head of the Royal House of Saxony.
Johannes was the only child of the Princess Mathilde of Saxony, the youngest daughter of Frederick Christian, Margrave of Meissen, thus a granddaughter of Frederick August III of Saxony who was deposed in 1918.
Mathilde's brothers did not have any children, and her elder sister Anna's issue with Roberto de Afif were deemed lower-born than the uncontested dynastic Prince Johannes.
Because his maternal uncles were already middle-aged and childless, Johannes was groomed from his youth to become the heir of the Royal House of Saxony.
However, Johannes died at seventeen on 21 August 1987 in a climbing accident.
He had gone on a climbing expedition on his own, telling his parents that he was headed to one site, but actually heading to a different, and riskier mountain.
When Johannes did not return home when expected, his worried parents notified the authorities.
Search parties were organized and helicopters were used to scour the region.
His lifeless body was spotted from a helicopter, thus bringing the search to a tragic end.
The loss of Johannes was a devastating blow to his desolated parents.
However, due to the tragedy, it also left his mother's family without a clear dynastic and eligible heir, and also left his father without a direct male heir.
Prince Johannes Heinrich of Saxe-Coburg and Gotha had fathered a daughter, Felicitas, from his previous marriage to Baroness Gabriele von Fürstenberg.
Friedrich Josias, Prince of Saxe-Coburg and Gotha
Friedrich Josias, Prince of Saxe- Coburg and Gotha( Friedrich Josias Carl Eduard Ernst Kyrill Harald; 29 November 1918 – 23 January 1998) was the head of the Ducal Family of Saxe- Coburg and Gotha and titular Duke of Saxe- Coburg and Gotha from 1954 until his death.
Andreas, Prince of Saxe-Coburg and Gotha
Andreas, Prince of Saxe- Coburg and Gotha, Duke of Saxony( given names:" Andreas Michael Friedrich Hans Armin Siegfried Hubertus"; born 21 March 1943) has been the head of the House of Saxe- Coburg and Gotha since 1998.
He is the grandson of Charles Edward, the last ruling duke of Saxe- Coburg and Gotha.
Kelly Rondestvedt
Kelly, Hereditary Princess of Saxe- Coburg and Gotha, Duchess of Saxony( born Kelly Jeanne Rondestvedt on 10 January 1975) is an American investment banker.
Through her marriage to Hubertus, Hereditary Prince of Saxe- Coburg and Gotha, the heir apparent to the defunct ducal throne of Saxe- Coburg and Gotha, she is a princess of the House of Saxe- Coburg and Gotha.

Question: Who is the maternal grandfather of Prince Johannes Of Saxe-Coburg And Gotha?