Georg Donatus, Hereditary Grand Duke of Hesse
Prince Georg Donatus, Hereditary Grand Duke of Hesse ("Georg Donatus Wilhelm Nikolaus Eduard Heinrich Karl", 8 November 1906 – 16 November 1937) was the first child of Ernest Louis, Grand Duke of Hesse and his second wife, Princess Eleonore of Solms-Hohensolms-Lich.
He was a nephew of Empress Alexandra, wife of Emperor Nicholas II of Russia.
Julia, Princess of Battenberg
Julia, Princess of Battenberg( previously Countess Julia von Hauke; – 19 September 1895) was the wife of Prince Alexander of Hesse and by Rhine, the third son of Louis II, Grand Duke of Hesse.
The daughter of a Polish general of German descent, she was not of princely origin.
She became a lady- in- waiting to Marie of Hesse, wife of the future Tsar Alexander II and a sister of Prince Alexander of Hesse and by Rhine, whom she married, having met him in the course of her duties.
The marriage of social unequals was deemed morganatic, but the Duke of Hesse gave her own title of nobility as Princess of Battenberg.
She was the mother of Alexander, Prince of Bulgaria, and is an ancestor of Charles, Prince of Wales, heir to the British throne, and to the current generations of the Spanish royal family.
Princess Irene of Hesse and by Rhine
Princess Irene of Hesse and by Rhine(" Irene Luise Marie Anne, Princess of Hesse and by Rhine", 11 July 1866 – 11 November 1953) was the third child and third daughter of Princess Alice of the United Kingdom and Louis IV, Grand Duke of Hesse and by Rhine.
Her maternal grandparents were Queen Victoria and Prince Albert of Saxe- Coburg and Gotha.
Her paternal grandparents were Prince Charles of Hesse and by Rhine and Princess Elizabeth of Prussia.
She was the wife of Prince Henry of Prussia, a younger brother of Wilhelm II, German Emperor and her first cousin.
The SS" Prinzessin Irene", a liner of the North German Lloyd was named after her.
Her siblings included Princess Victoria of Hesse and by Rhine, wife of Prince Louis of Battenberg, Grand Duchess Elizabeth Feodorovna of Russia, wife of Grand Duke Sergei Alexandrovich of Russia, Ernest Louis, Grand Duke of Hesse and by Rhine, and Empress Alexandra Feodorovna of Russia, wife of Tsar Nicholas II of Russia.
Like her younger sister, the empress, Irene was a carrier of the hemophilia gene, and Irene would lose her sisters Alix and Elisabeth in Russia to the Bolsheviks.
Margaret, Princess of Hesse and by Rhine
Margaret, Princess of Hesse and by Rhine( born Margaret Campbell Geddes, 18 March 1913 – 26 January 1997) was the wife of Louis, Prince of Hesse and by Rhine, the last prince of the House of Hesse- Darmstadt.
Born in Ireland, she became a noted art patron in her adopted homeland of Germany.
Prince Ludwig of Hesse and by Rhine
Prince Ludwig of Hesse and by Rhine
(Ludwig Ernst Andreas Prinz und Landgraf von Hessen), (25 October 1931 – 16 November 1937), was the eldest son of Georg Donatus, Hereditary Grand Duke of Hesse and Princess Cecilie of Greece and Denmark, an older sister of Prince Philip, Duke of Edinburgh.
He was the first great-great-great-grandchild of Queen Victoria.
He was killed at age six in an airplane crash in 1937.
He, his parents, younger brother Alexander, and grandmother Grand Duchess Eleonore were flying to London to attend the wedding of his uncle Prince Ludwig to Margaret Geddes.
The plane crashed into a factory chimney near Ostend, Belgium.
Louis II, Grand Duke of Hesse
Louis II( 26 December 1777 – 16 June 1848) was Grand Duke of Hesse and by Rhine from 6 April 1830 until 5 March 1848, resigning during the German Revolution of 1848.
He was the son of Louis I, Grand Duke of Hesse, and Princess Louise of Hesse- Darmstadt.
Princess Louise of Hesse-Darmstadt (1761–1829)
Louise Henriette Karoline of Hesse- Darmstadt( 15 February 1761 – 24 October 1829), was the first Grand Duchess of Hesse and by Rhine by marriage.
Prince Friedrich of Hesse and by Rhine
Prince Friedrich of Hesse and by Rhine( Friedrich Wilhelm August Victor Leopold Ludwig; 7 October 1870 – 29 May 1873) was the haemophiliac second son of Louis IV, Grand Duke of Hesse, and Princess Alice of the United Kingdom, one of the daughters of Queen Victoria.
He was also a maternal great- uncle of Prince Philip, Duke of Edinburgh through his eldest sister Princess Victoria of Hesse and by Rhine.
Prince Charles of Hesse and by Rhine
Prince Charles of Hesse and by Rhine (23 April 1809 - 20 March 1877) was the second surviving son of Louis II, Grand Duke of Hesse and Wilhelmine of Baden.
Louis III, Grand Duke of Hesse
Louis III, Grand Duke of Hesse and by Rhine( 9 June 1806, Darmstadt – 13 June 1877, Seeheim) was Grand Duke of Hesse and by Rhine from 1848 until his death in 1877.

Question: Who is the paternal grandfather of Prince Ludwig Of Hesse And By Rhine?
Answer: Ernest Louis, Grand Duke of Hesse