Beatrice of Luxembourg
Beatrice of Luxembourg( 1305 – 11 November 1319), was by birth member of the House of Luxembourg and by marriage Queen of Hungary.
She was the youngest child of Henry VII, Holy Roman Emperor and his wife, Margaret of Brabant.
Her two siblings were John of Luxembourg and Marie of Luxembourg, Queen of France.
Henry III, Count of Luxembourg
Henri III, Count of Luxembourg( died 1096) was count of Luxembourg( 1086 – 1096), in succession to his father Conrad.
His mother was Clementia of Aquitaine.
Henry III was the first count known to have established his permanent residence in Luxembourg castle.
In a document from the year 1089, he is referred to as comes Henricus de Lutzeleburg, which also makes him the first documented count of Luxembourg.
He never married and was succeeded by his brother William.
Conrad I, Count of Luxembourg
Conrad I (c. 1040 – 8 August 1086), Count of Luxembourg, was the first count of Luxembourg (1059–1086), succeeding his father Giselbert of Luxembourg.
He was embroiled in an argument with the archbishop of Trier as to the abbaye Saint-Maximin in Trier which he had avowed.
The archbishop excommunicated him and Conrad had to make honourable amends and set out on pilgrimage for Jerusalem to have his excommunication lifted.
He died in Italy on the return journey.
He founded many abbeys:
Conrad II, Count of Luxembourg
Conrad II of Luxembourg( died 1136) was count of Luxembourg( 1131 – 1136), in succession to his father William I of Luxembourg.
His mother was Mathilde or Luitgarde of Northeim.
He married Ermengarde, daughter of count Otto II, Count of Zutphen.
Conrad II died without a male heir, and so the county of Luxembourg reverted to the Holy Roman Emperor.
The emperor in turn did not wish the county to be rule by Conrad's closest relative Henri de Grandpré, who was a French lord and so might align the county with the kingdom of France, and so granted it to Henry of Namur, a cousin of Conrad's.
Giselbert of Luxembourg
Giselbert of Luxembourg (c. 1007 – 14 August 1059) was count of Salm and of Longwy, then count of Luxemburg from 1047 to 1059.
He was a son of Frederick of Luxembourg, count of Moselgau, and perhaps of Ermentrude of Gleiberg.
At first count of Salm and of Longwy, on his brother Henry II's death he inherited the county of Luxembourg, as well as providing the income for the abbeys of Saint-Maximin in Trier and Saint-Willibrord in Echternach.
He got into an argument with the archbishop of Trier Poppon as to the abbaye Saint-Maximin, which was arbitrated by his brother Adalbero III, bishop of Metz.
In 1050, since the population of the town of Luxembourg had risen considerably, he expanded the city by building a new fortified wall around it.
By an unknown wife, he had:
Kaya Alp
Kaya Alp was, according to Ottoman tradition, the son of Kızıl Buğa and the father of Suleyman Shah, who was, in turn, the grandfather of Ertuğrul, and the great grandfather of the Ottoman Empire founder, Osman I.
William, Count of Luxembourg
William I, Count of Luxembourg( 1081–1131) was count of Luxembourg( 1096 – 1131), in succession to his elder brother Henry III of Luxembourg.
They were both sons of Conrad and Clementia of Aquitaine.
William was the first of his family to use the title" count of Luxembourg" in his documents.
Like his predecessors, he was embroiled in debates with the archbishop of Trier Bruno in 1122 and 1127, leading to William's excommunication.
Around 1105 he married Mathilde or Luitgarde of Northeim, daughter of Kuno, count of Beichlingen, and had three children:
Alice of Namur
Alice of Namur( died July 1169 at Valenciennes) was the daughter of Godfrey I, Count of Namur and Ermesinde, Countess of Luxembourg and Longwy the daughter of Conrad I of Luxembourg.
Her father married her off to Baldwin IV, Count of Hainault around 1130.
Gislebert of Mons described her as having" a graceful body and a beautiful face".
Her son was the heir of Namur when her brother Henry IV of Luxembourg died in 1196.
Her children with Baldwin IV of Hainaut were:
She was buried inside Saint Waltrude Collegiate Church.
Marie of Luxembourg, Queen of France
Marie of Luxembourg( 1304 – 26 March 1324), was by birth member of the House of Luxembourg and by marriage Queen of France and Navarre.
She was the daughter of Henry VII, Holy Roman Emperor and Margaret of Brabant.
Her two siblings were John of Luxembourg and Beatrice of Luxembourg, Queen of Hungary.
Dietrich, Count of Plötzkau
Dietrich( 11th century), Count of Plötzkau', son of Bernhard I von Kakelingen, Count of Harzgau and his wife Ida of Querfurt.
Little is known about Dietrich or his ancestors other than their familial relations.
Dietrich was the brother of Gebhard of Supplinburg, a Saxon count, who was the father of Lothair II, Holy Roman Emperor.
Ida, the mother of Dietrich, was niece of Saint Bruno of Querfurt.
Dietrich married Mathilde von Walbeck, daughter of Conrad, Count of Walbeck.
Dietrich and Mathilde had four children:
Upon his death, Dietrich was succeed as Count of Plötzkau by his son Helperich.

Question: Who is Conrad I, Count Of Luxembourg's paternal grandfather?
Answer: Frederick of Luxembourg