John I, Count of Dreux
John I of Dreux( 1215–1249), Count of Dreux and Braine, was the son of Robert III of Dreux and Annora( Aenor) of Saint- Valéry.
Robert II, Count of Dreux
Robert II of Dreux (1154 – 28 December 1218), Count of Dreux and Braine, was the eldest surviving son of Robert I, Count of Dreux, and Agnes de Baudemont, countess of Braine, and a grandson of King Louis VI of France.
He participated in the Third Crusade, at the Siege of Acre and the Battle of Arsuf.
He took part in the war in Normandy against the Angevin Kings between 1193 and 1204.
Count Robert had seized the castle of Nonancourt from Richard I of England while he was imprisoned in Germany in late 1193.
The count also participated in the Albigensian Crusade in 1210.
In 1214 he fought alongside King Philip Augustus at the Battle of Bouvines.
Philippa of Dreux
Philippa of Dreux, Dame de Coucy (1192–1242) was a daughter of Robert II of Dreux and his second wife Yolande de Coucy.
John III, Count of Dreux
John III( – 1331), Count of Dreux, was the second son of John II of Dreux and of Jeanne of Beaujeu.
Yolande of Dreux, Duchess of Burgundy
Yolande of Dreux( 1212–1248) was Duchess of Burgundy as the first wife of Hugh IV of Burgundy( duke of Burgundy between 1218 and 1271).
She was the daughter of Count Robert III" Gasteblé" of Dreux and of Braine, and his wife Alianor de St. Valéry.
Peter, Count of Dreux
Peter,( 1298 – 3 November 1345), Count of Dreux, was the youngest son of John II, Count of Dreux and Jeanne of Beaujeu.
He participated in the war of Philip VI of France, fighting against the Flemish who were revolting against their count, and he fought at the Battle of Cassel in 1328.
Robert III, Count of Dreux
Robert III of Dreux (1185–1234), Count of Dreux and Braine, was the son of Robert II, Count of Dreux, and Yolanda de Coucy.
He was given the byname Gasteblé (lit. wheat-spoiler) when he destroyed a field of wheat while hunting in his youth.
Along with his brother Peter, Duke of Brittany he fought with future Louis VIII of France in 1212 at Nantes and was captured there during a sortie.
Exchanged after the Battle of Bouvines for William Longsword, Earl of Salisbury, he fought in the Albigensian Crusade, besieging Avignon in 1226.
He was a supporter of Blanche of Castile during her regency after the death of Louis VIII in 1226.
In 1210 he married Alianor de St. Valéry (1192–15 Nov 1250) and they had several children:
Robert V, Count of Dreux
Robert V of Dreux( – 22 March 1329), Count of Dreux and Braine, was the eldest son of John II of Dreux.
His mother was Peronelle de Sully, the principal lady of Joan II, Countess of Burgundy's household.
Robert was a supporter of Joan II's husband, Philip V of France.
He succeeded his father as Count of Dreux in 1309 and reigned until his death in 1329.
He married Marie d' Enghien in April 1321, but died without issue on 22 March 1329 in Braine and was succeeded by his brother, John III of Dreux.
Adèle of Dreux
Adèle of Dreux( 1145 – aft. 1210) was a member of Norman French nobility, daughter of Robert I, Count of Dreux and his second wife Hawise of Salisbury.
She married Valéran III, Count of Breteuil on 24 June 1156, and had the following issue:
After Valéran's death in 1162, she married secondly Guy II of Châtillon and had:
She married thirdly John I de Thorotte and had:
Her final marriage was to Ralph, Count of Soissons, with whom she had: Adèle died after 1210.
Louis I, Count of Nevers
Louis I( 1272 – 22 July 1322) was" suo jure" Count of Nevers and" jure uxoris" Count of Rethel.
Louis was a son of Robert III, Count of Flanders, and Yolande, Countess of Nevers.
He succeeded his parents as Count of Nevers.
In December 1290, he married Joan, Countess of Rethel, and thus became her co-ruler in the County of Rethel.
They had two children:
He died in Paris shortly before his father and thus never succeeded his father as Count of Flanders.

Question: Who is Robert Iii, Count Of Dreux's paternal grandfather?
Answer: Robert I, Count of Dreux