Question: Who is John Of Luxembourg, Count Of Soissons's maternal grandfather?

Knowledge 1: John of Luxembourg, Count of Soissons
John of Luxembourg (died 22 June 1476) was Count of Marle and Count of Soissons between 1462 and 1476, Lord of Dunkirk, Gravelines and Bourbourg.He was the eldest son of Louis de Luxembourg, Count of Saint-Pol and Jeanne de Bar, Countess of Marle and Soissons.<br>When his mother died in 1462, he became Count of Marle and Soissons.<br>John became a Knight in the Order of the Golden Fleece in 1473.<br>
When his father was beheaded for treason in 1475, John wasn't able to inherit his lands, because they were confiscated.John was killed one year later at the Battle of Morat.He never married and his lands went to his younger brother Peter. [SEP] Knowledge 2: Jeanne of Bar, Countess of Marle and Soissons
Jeanne de Bar, suo jure Countess of Marle and Soissons, Dame d'Oisy, Viscountess of Meaux, and Countess of Saint-Pol, of Brienne, de Ligny, and Conversano (1415 – 14 May 1462) was a noble French heiress and Sovereign Countess.She was the only child of Robert of Bar, Count of Marle and Soissons, Sire d'Oisy, who was killed at the Battle of Agincourt when she was a baby, leaving her the sole heiress to his titles and estates.In 1430, at the age of fifteen, Jeanne was one of the three women placed in charge of Joan of Arc when the latter was a prisoner in the castle of John II of Luxembourg, Count of Ligny, Jeanne's stepfather.She was the first wife of Louis of Luxembourg, Count of Saint-Pol, of Brienne, de Ligny, and Conversano, Constable of France.From their marriage descended Mary, Queen of Scots, King Henry IV of France and the subsequent Bourbon kings of France.
Knowledge 1: John of Luxembourg, Count of Soissons
John of Luxembourg (died 22 June 1476) was Count of Marle and Count of Soissons between 1462 and 1476, Lord of Dunkirk, Gravelines and Bourbourg.He was the eldest son of Louis de Luxembourg, Count of Saint-Pol and Jeanne de Bar, Countess of Marle and Soissons.<br>When his mother died in 1462, he became Count of Marle and Soissons.<br>John became a Knight in the Order of the Golden Fleece in 1473.<br>
When his father was beheaded for treason in 1475, John wasn't able to inherit his lands, because they were confiscated.John was killed one year later at the Battle of Morat.He never married and his lands went to his younger brother Peter. [SEP] Knowledge 2: Margaret, Countess of Soissons
Margaret (or Margaretha) of Soissons (died ca. 1350) was ruling Countess of Soissons in 1305-1344.She was the only daughter of Hugh, Count of Soissons, and Johanna of Argies.In 1306 she succeeded her father as Countess of Soissons.Margaret was married to John of Beaumont, son of John II, Count of Holland.Margaret and John had five children:
Upon their marriage, John became Count of Soissons, "jure uxoris".
Knowledge 1: Jeanne of Bar, Countess of Marle and Soissons
Jeanne de Bar, suo jure Countess of Marle and Soissons, Dame d'Oisy, Viscountess of Meaux, and Countess of Saint-Pol, of Brienne, de Ligny, and Conversano (1415 – 14 May 1462) was a noble French heiress and Sovereign Countess.She was the only child of Robert of Bar, Count of Marle and Soissons, Sire d'Oisy, who was killed at the Battle of Agincourt when she was a baby, leaving her the sole heiress to his titles and estates.In 1430, at the age of fifteen, Jeanne was one of the three women placed in charge of Joan of Arc when the latter was a prisoner in the castle of John II of Luxembourg, Count of Ligny, Jeanne's stepfather.She was the first wife of Louis of Luxembourg, Count of Saint-Pol, of Brienne, de Ligny, and Conversano, Constable of France.From their marriage descended Mary, Queen of Scots, King Henry IV of France and the subsequent Bourbon kings of France. [SEP] Knowledge 2: Margaret, Countess of Soissons
Margaret (or Margaretha) of Soissons (died ca. 1350) was ruling Countess of Soissons in 1305-1344.She was the only daughter of Hugh, Count of Soissons, and Johanna of Argies.In 1306 she succeeded her father as Countess of Soissons.Margaret was married to John of Beaumont, son of John II, Count of Holland.Margaret and John had five children:
Upon their marriage, John became Count of Soissons, "jure uxoris".

Answer: Robert of Bar, Count of Marle and Soissons