Nicholas I of Saint Omer
Nicholas I of Saint Omer was a French knight who in the aftermath of the Fourth Crusade became a lord in the Frankish Duchy of Athens.
Nicholas was a younger son of William IV of Saint Omer, castellan of Saint-Omer in northern France, and Ida of Avesnes.
Ida's brother James of Avesnes took part in the Fourth Crusade (1203–04) and accompanied Boniface of Montferrat in the conquest and partition of Greece in its aftermath.
He was rewarded with possessions in Euboea, but was dead by August 1205.
Nicholas remained in his native region until ca. 1208, after which he and his brother James came to Greece, where they received a fief at Erimokastro, the site of ancient Thespiae, west of Thebes.
According to F. Van Tricht, the fief may have formed part of the Templar possessions that were confiscated ca. 1209 by the Latin Emperor Henry of Flanders.
In 1210, he was among the signatories of the concordat with the Latin Church at the Second Parliament of Ravennika.
Nicholas later married Margaret of Hungary, the widow of Boniface of Montferrat, who died in 1207.
It is unclear when the marriage took place: traditional accounts mention that Nicholas died already in 1212 or 1214, but F. Van Tricht dates the marriage to after 1217.
With Margaret he had two sons, Bela and William.
Bela would marry Bonne de La Roche, the sister of Guy I, the Duke of Athens, become lord of one half of Thebes, and lay the foundations for the rise of the Saint Omer family to a prominent position in Frankish Greece.
William of Saint Omer (son of Nicholas I)
William of Saint Omer was a French knight, descended from a Fauquembergues family who were castellans of the eponymous castle of Saint- Omer.
His father, Nicholas I of Saint Omer, received lands in Boeotia in the aftermath of the Fourth Crusade.
He later married Margaret of Hungary, the widow of Boniface of Montferrat, Lord of Thessalonica( died 1207).
It is unclear when the marriage took place: traditional accounts mention that Nicholas died already in 1212 or 1214, but F. Van Tricht dates the marriage to after 1217.
William was the younger son of the couple, he had an elder brother Bela of Saint Omer.
While Bela received one half of Thebes as dowry from his marriage, William and his mother moved to the Kingdom of Hungary, where Béla IV was the King, also a grandson of Béla III, like William.
Following his mother's death sometime after 1223, William inherited her estates in Syrmia and Macsó.
He participated in the Battle of Mohi, following this he belonged to the companion of Béla IV who had fled to Dalmatia, escaping before the Mongols.
William was" ispán" of Kraszna County in 1241.
From 1241 until his death, he served as Master of the Horse.
Béla IV betrothed William to his second eldest daughter Margaret( not to be confused with Saint Margaret of Hungary), however both persons died by 1242.
According to his epitath at the Cathedral of Saint Domnius, William died in April 1242 in Trogir, where the royal family resided until the Mongol occupation.
Bela of Saint Omer
Bela of Saint Omer was a French knight, descended from a Fauquembergues family who were castellans of the eponymous castle of Saint-Omer.
His father, Nicholas I of Saint Omer, received lands in Boeotia in the aftermath of the Fourth Crusade.
He later married Margaret of Hungary, the widow of Boniface of Montferrat, Lord of Thessalonica (died 1207).
It is unclear when the marriage took place: traditional accounts mention that Nicholas died already in 1212 or 1214, but F. Van Tricht dates the marriage to after 1217.
Bela, who was named after his maternal grandfather, Béla III of Hungary, was the eldest son of the couple, and was followed by his brother William.
In 1240, Bela married the sister of the Lord of Athens and Thebes, Guy I de la Roche.
As part of her dowry, he received one half of Thebes as his domain.
They had three sons, Nicholas II of Saint Omer (d. 1294), who succeeded in Thebes, Otho of Saint Omer (d. before 1299), and John of Saint Omer (d. 1311), who became Marshal of the Principality of Achaea.
Bela of Britonia
Bela of Britonia(?- 675-?) was a medieval Galician clergyman.
Jean Six
Jean Six( 1533 – 1586) was a theologian and bishop of Saint- Omer.
William V of Saint Omer
William V of Saint Omer( ca. 1171 – ca. 1246) was the castellan of Saint- Omer from 1192 until his death, as well as Lord of Beaurain and Fauquembergues.
Born in ca. 1171, he was the eldest son of William IV of Saint Omer and Ida of Avesnes.
He is attested in charters issued by his father from 1185 on, and some time between 1190 and 1192 he succeeded his father, who had died in the Holy Land.
He is attested in numerous charters and deeds of property as well as donation to the Church over the next decades.
He repeatedly pledged his loyalty to King Philip Augustus during the latter's conflicts with his neighbours, and is occasionally mentioned among the Flemish feudatories of the French court.
He married Imagina of Looz, daughter of Gerard II, Count of Looz.
The marriage was childless, and after his death( sometime between March 1246 and August 1247) he was succeeded by his sole surviving brother, William VI of Saint Omer.
Otho of Saint Omer
Otho of Saint Omer was the lord of half of Thebes in Frankish Greece from 1294 to ca. 1299.
He was a younger son of Bela of Saint Omer and Bonne de la Roche, sister of the Lord of Athens and Thebes, Guy I de la Roche.
Upon their marriage, in 1240, Guy gave Bela the lordship over half of Thebes.
Otho participated, along with his brothers Nicholas II and John, in the War of the Euboeote Succession in the ranks of the coalition of most of the princes of Frankish Greece, who opposed the expansionist policies of the Prince of Achaea, William II of Villehardouin.
Otho was married to Margarita da Verona.
After Nicholas II's death in 1294, he succeeded him as lord of one half of Thebes until his own death, sometime before 1299.
William VI of Saint Omer
William VI of Saint Omer was the castellan of Saint- Omer and lord of Fauquembergues briefly in ca. 1246/ 7.
The genealogist Baldwin of Avesnes records him as a son of William V of Saint Omer, but Arthur Giry has him rather a younger brother of the latter, i.e. he was one of the eleven children of William IV of Saint Omer and Ida of Avesnes.
He is first attested in April 1207, and appears thereafter in various charters and documents, in which from 1218 on he appears as lord of Pitgam and later of Berkin.
He succeeded his brother sometime between March 1246 and his own only attestation as castellan, in August 1247.
Very little is known of his tenure, which apparently was very brief; Baldwin of Avesnes merely records that he went on Crusade, where he died.
He was succeeded by his eldest sister Beatrice and her son William of Renenghes by 1251.
Godfrey de Saint-Omer
Godfrey of Saint- Omer( also known as Gaufred, Godefroi, or Godfrey de St Omer, Saint Omer) was a Flemish knight and one of the founding members of the Knights Templar in 1119.
He is said to have come from the family of the Lords of Saint- Omer( in today's northern France), possibly the son of William I, Lord of Saint Omer and Melisende de Piquigny.
There are conflicting reports as to Godfrey's relationship to William and Hugh of Fauquembergues.
Chronologically Godfrey may have been Hugh's brother but it is also said that he was Hugh's son.
On the list of crusaders, a Gauthier de Saint- Omer is listed, which could be a mistake for Gaufred( Gauthier de Saint- Omer was not yet born).
Therefore, Godfrey probably came to Jerusalem in 1099 with William I and Hugh.
According to legend, Hugues de Payens( the first Grand- Master of the Templars) and Godfrey were so poor that between the two of them they had only one horse, and this gave rise to the famous image on the seal of the Templars, of two men riding a single horse.
John of Saint Omer
John of Saint Omer( Jean de Saint- Omer) was Marshal and baron of a third of Akova in the Principality of Achaea.

Question: Who is the paternal grandfather of Bela Of Saint Omer?
Answer: William IV of Saint Omer