Louis I, Count of Loon
Louis I, Count of Loon( Looz)( after 1107 – 11 August 1171) was the Count of Loon, which he inherited from his father.
He ruled from approximately 1139 until his death.
Charlotte of Lorraine
Charlotte de Lorraine- Armagnac( 6 May 1678 – 21 January 1757) was a Princess of Lorraine by birth and daughter of Louis, Count of Armagnac.
She was known as" Mademoiselle d' Armagnac" and died unmarried.
Gilbert, Count of Montpensier
Gilbert de Bourbon, Count of Montpensier( 1443 – 15 October 1496, Pozzuoli) was the son of Louis de Bourbon and Gabrielle La Tour, Count of Montpensier and Dauphin d'Auvergne.
He was appointed to the Order of Saint Michael by Charles VIII in October 1483.
Louis, Duke of Montpensier
Louis de Bourbon (10 June 1513 – 23 September 1582) was the second Duke of Montpensier.
He was the great great grandfather of "la Grande Mademoiselle".
Louis II, Count of Montpensier
Louis de Bourbon, Count of Montpensier( 1483 – August 14, 1501, Naples) was the son of Gilbert, Count of Montpensier and Claire Gonzaga.
He was Count of Montpensier and Clermont- en- Auvergne and Dauphin d'Auvergne from 1496 to his death.
He died unmarried and was succeeded by his brother Charles III, Duke of Bourbon.
Philipp Louis, Count of Erbach-Erbach
Philipp Louis, Count of Erbach- Erbach( 10 June 1669 – 17 June 1720), was a German prince member of the House of Erbach and ruler over Erbach, Freienstein, Wildenstein, Michelstadt and Breuberg.
Born in Erbach, he was the third child and eldest son of George Louis I, Count of Erbach- Erbach and his wife Countess Amalia Katharina of Waldeck- Eisenberg, a daughter of Philipp Dietrich, Count of Waldeck- Eisenberg.
Marie, Duchess of Auvergne
Marie of Berry (c. 1375 – June 1434) was "suo jure" Duchess of Auvergne and Countess of Montpensier in 1416-1434.
She was the daughter of John, Duke of Berry, and Joanna of Armagnac.
She was married three times.
She acted as administrator of the Duchy of Bourbon for her third spouse
John I, Duke of Bourbon, during his imprisonment in England after he was captured following the French defeat at the Battle of Agincourt in 1415, until 1434.
William XII, Count of Auvergne
William XII of Auvergne( 1300 – 1332) was Count of Auvergne and Count of Boulogne between 1325 and 1332.
He was the eldest son of Robert VII of Auvergne and Blanche of Bourbon, daughter of Robert, Count of Clermont.
He married Margaret of Évreux( 1307 – 1350), daughter of Louis, Count of Évreux and Margaret of Artois .< br>
William died young and had only one daughter:
Louis I, Count of Montpensier
Louis de Bourbon (1405 – May 1486) was the third son of John I, Duke of Bourbon and Marie, Duchess of Auvergne.
He was Count of Montpensier, Clermont-en-Auvergne and Sancerre and Dauphin of Auvergne and was a younger brother of Charles I of Bourbon.
He founded the Bourbon-Montpensier branch of the House of Bourbon, who would eventually take over the Duchy in 1505.
Louis, Prince of La Roche-sur-Yon
Louis de Bourbon( 1473 – 1520) styled as the" Prince of La Roche- sur- Yon" was born in 1473.
He was the son of John II, Count of Vendôme and Isabel de Beauveau.
He married his cousin, Louise de Bourbon, Duchess of Montpensier, eldest daughter of Gilbert of Bourbon, Count of Montpensier and Clara Gonzaga, on 21 March 1504, by whom he had three children.
He died in 1520.

Question: Who is Louis I, Count Of Montpensier's maternal grandfather?
Answer: John, Duke of Berry