Charles Henri, Prince of Commercy
Charles Henri of Lorraine( 17 April 1649 – 14 January 1723) was the legitimated son of Charles IV, Duke of Lorraine, and Béatrix de Cusance.
He was given the Principality of Commercy in 1708 by his cousin Leopold, Duke of Lorraine.
He was also the Count of Falkenstein.
Ida of Lorraine
Ida of Lorraine( also referred to as Blessed Ida of Boulogne)( c. 1040 – 13 April 1113) was a saint and noblewoman.
She was the daughter of Godfrey III, Duke of Lower Lorraine and his wife Doda.
Ida's grandfather was Gothelo I, Duke of Lorraine and Ida's brother was Godfrey IV, Duke of Lower Lorraine.
Renata of Lorraine
Renata of Lorraine( 20 April 1544 – 22 May 1602) was by birth a member of the House of Lorraine and by marriage Duchess of Bavaria.
Born in Nancy, France, she was the second child and eldest daughter of Francis I, Duke of Lorraine and Christina of Denmark.
Her paternal grandparents were Antoine, Duke of Lorraine and Renée of Bourbon- Montpensier and her maternal grandparents were Christian II of Denmark and Isabella of Austria.
Claude Françoise de Lorraine
Claude of Lorraine (6 October 1612 – 2 August 1648) was a daughter of Henry II, Duke of Lorraine, and Margerita Gonzaga, her sister was Nicole, Duchess of Lorraine.
She married her first cousin and was the Duchess of Lorraine by marriage.
Bertha, Duchess of Lorraine
Bertha of Lorraine( or Bertha of Swabia)( b.c. 1123/30 – d. 1194/ 5) was a member of the Hohenstaufen dynasty.
She was the daughter of Frederick II, Duke of Swabia and, through marriage to Matthias I duke of Lorraine, she was duchess of Lorraine( c.1138-1176).
Dorothea of Lorraine
Dorothea of Lorraine( 24 May 1545 – 2 June 1621), was by birth a member of the House of Lorraine and by marriage to Eric II, Duke of Brunswick- Lüneburg, Duchess of Brunswick- Lüneburg- Calenburg.
Born at the Château de Deneuvre, she was the third child and second daughter of Francis I, Duke of Lorraine and Christina of Denmark.
Her paternal grandparents were Antoine, Duke of Lorraine and Renée of Bourbon- Montpensier and her maternal grandparents were Christian II of Denmark and Isabella of Austria.
Nicolas, Duke of Mercœur
Nicolas of Lorraine, Duke of Mercœur (16 October 1524 – 23 January 1577) was the second son of Antoine, Duke of Lorraine and Renée de Bourbon.
Gothelo I, Duke of Lorraine
Gothelo (or Gozelo) (– 19 April 1044), called the Great, was the duke of Lower Lorraine from 1023 and of Upper Lorraine from 1033.
He was also the margrave of Antwerp from 1005 (or 1008) and count of Verdun.
Gothelo was the youngest son of Godfrey I, Count of Verdun, and Matilda Billung, daughter of Herman, Duke of Saxony.
On his father's death, he received the march of Antwerp and became a vassal of his brother, Godfrey II, who became duke of Lower Lorraine in 1012.
He succeeded his brother in 1023 with the support of the Emperor Henry II, but was opposed until Conrad II forced the rebels to submit in 1025.
When the House of Bar, which ruled in Upper Lorraine, became extinct in 1033, with the death of his cousin Frederick III, Conrad made him duke of both duchies, so that he could assist in the defence of the territory against Odo II, count of Blois, Meaux, Chartres, and Troyes (the later Champagne).
In the battle at Bar on 15 November 1037, Gothelo dealt a decisive blow to Odo, who was trying to create an independent state between France and Germany.
Odo died in the battle.
Gothelo died on 19 April 1044 and was buried in the Abbey Church of Bilzen.
His son Godfrey succeeded in Upper Lorraine, but the Emperor Henry III refused to give him the duchy of Lower Lorraine as well.
When Godfrey showed disagreement with the imperial decision, Henry III threatened to pass the duchy to Godfrey's incompetent brother Gothelo.
This caused a long rebellion in Lotharingia between the allies of Godfrey (the counts of Flanders and Leuven) and imperial forces (1044–1056).
Matilda of Saxony, countess of Flanders
Matilda of Saxony (c. 935-942 – 25 May 1008) was duchess of Saxony, countess of Saxony, princess of Saxony, and countess of Flanders.
She was the daughter of Hermann Billung and Hildegard von Westerburg.
She was born in Herzogtum Sachsen, Ostenfrankenreich, now part of modern Germany.
Matlida was the sister of Swanhilde of Saxony and Bernard I, duke of Saxony; and half sister of Liudger von Sachsen, Graf von Lesum und Westfalen and Imma Von Billung, Abbess of Hereford.
Matilda was the wife of Baldwin III, count of Flanders, with whom she had a son Arnulf II the Young, count of Flanders.
After Baldwin's death, Matilda married Godefroi
I
the Captive, count of Ardennes, with whom she had eleven children:
Adelaide d'Ardennes, Duchess of Lorraine; Comte van Verdun Godefroy Herzog von Niederlothringen, II; Gerberge de Verdun, comtesse; Hermann, comte de Verdun et d'Enham; Gothelo
I "the Great", duke of Lorraine; Irmgard, comtesse de Verdun; Roger de Verdun, Governor of Ambriences Castle; Frédéric de Verdun; Regilla de Verdun; comte Adalberto Evêque de Vermandois, II and Ermentrude von Lothringen de Verdun.
Matilda died on 25 May 1008 and was buried in Ghent, East Flanders, Belgium.
Elisabeth Therese of Lorraine
Elisabeth Therese of Lorraine( 15 October 1711 – 3 July 1741) was born a Princess of Lorraine and was the last queen consort of Charles Emmanuel III of Sardinia.
The sister of Francis Stephan, Duke of Lorraine, she died as a result of giving birth to Benedetto of Savoy.

Question: Who is Gothelo I, Duke Of Lorraine's maternal grandfather?
Answer: Hermann Billung