Guy II, Count of Soissons
Guy II( d. 1057), son of Renaud I, Count of Soissons, and his wife( name unknown), widow of Hilduin III, Count of Montdidier.
Count of Soissons.
Guy was identified as Count of Soissons in 1042 in a charter in which Gaunilo of Marmoutiers, the treasurer of St. Martin, denoted property.
Guy died with his father in 1057 at the siege of Soissons.
It is not known whether or not Guy was married and no children are recorded.
Upon his death, his sister Adelaide assumed the countship of Soissons.
Margaret, Countess of Brienne
Marguerite d' Enghien, suo jure Countess of Brienne and of Conversano," suo jure" Heiress of Enghien, and Lady of Beauvois( born 1365), was a wealthy noblewoman from the County of Hainaut in her own right, having inherited the counties of Brienne and of Conversano, and the Lordship of Enghien from her father Louis of Enghien on 17 March 1394.
She was the wife of John of Luxembourg, Sire of Beauvois and the mother of Peter of Luxembourg, Count of Saint- Pol, Count of Brienne and of Conversano who inherited her fiefs, and John II of Luxembourg, Count of Ligny.
Nocher II, Count of Soissons
Nocher II( d. 1019), Count of Bar- sur- Aube, Count of Soissons.
He was the son of Nocher I, Count of Bar-sur- Aube.
Nocher ’s brother Beraud( d. 1052) was Bishop of Soissons.
Nocher became Count of Soissons, jure uxoris, upon his marriage to Adelise, Countess of Soissons.
Nocher and Adelisa had three children: Nocher ’s son and namesake became Count of Bar-sur- Aube upon his death, and the countship of Soissons reverted to his wife.
His son Renaud would eventually become the Count of Soissons.
Adelaide, Countess of Soissons
Adelaide( died 1105), was sovereign Countess of Soissons from 1057 until 1105.
She was the daughter of Renaud I, Count of Soissons, and his wife, whose name is unknown, widow of Hilduin III, Count of Montdidier..
Adelaide became ruler of the County of Soissons upon the death of her father and brother, Guy II, Count of Soissons, in 1057.
Adelaide married William Busac, Count of Eu, grandson of Richard I, Duke of Normandy.
Adelaide and William had five children: William Busac became Count of Soissons," de jure uxoris", upon their marriage.
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".
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
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When his mother died in 1462, he became Count of Marle and Soissons.<br
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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.
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.
John V, Count of Soissons
John V( 21 March 1281 – 1304), son of John IV, Count of Soissons, and his wife Marguerite of Rumigny.
Count of Soissons.
John inherited the countship of Soissons from his father in 1302.
Nothing is known about his brief rule of the county.
He never married and died with no heirs.
Upon his death, his brother Hugh became Count of Soissons.
John III, Count of Soissons
John III (d. before 8 October 1286), son of John II, Count of Soissons, and Marie de Chimay.
Count of Soissons and Seigneur of Chimay.
John inherited the countship of Soissons upon his father’s death in 1272.
John married Marguerite de Montfort, daughter of Amaury, Count of Montfort, and his wife Beatrix de Viennois.
John and Marguerite had five children:
John was succeeded as Count of Soissons by his son and namesake upon the former’s death.
William Busac
William Busac( 1020- 1076), son of William I, Count of Eu, and his wife Lesceline.
Count of Eu, Count of Soissons," de jure uxoris".
William was given the nickname Busac by the medieval chronicler Robert of Torigni.
William appealed to King Henry
I of France, who gave him in marriage Adelaide, the heiress of the county of Soissons.
Adelaide was daughter of Renaud I, Count of Soissons, and Grand Master of the Hotel de France.
William then became Count of Soissons in right of his wife.
William and Adelaide had four children:
His son Renaud became Count of Soissons upon William ’s death, and he was succeeded by his brother John.

Question: Who is John Of Luxembourg, Count Of Soissons's maternal grandfather?
Answer: Robert of Bar, Count of Marle and Soissons