Joan of Navarre (regent)
Joan of Navarre( 1382 – July 1413) was the heir presumptive to the throne of Navarre in 1402 – 1413, and regent of Navarre in the absence of her father in 1409 – 1411.
She was the eldest child of King Charles III of Navarre by his wife Eleanor, daughter of King Henry II of Castile.
Manu Aierdi
Manuel Aierdi Olaizola( born 13 January 1967) is a Basque economist, politician, Minister of Economic Development and Business of Navarre and a member of the Parliament of Navarre.
He was previously First Vice President of Navarre.
René I, Viscount of Rohan
René I de Rohan,( 1516–1552) 18th Viscount of Rohan, Viscount and Prince de Léon, and Marquis de Blain married Isabella of Navarre daughter of jure uxoris King John III of Navarre and Catherine of Navarre, Queen of Navarre.
Blanche of Navarre, Duchess of Brittany
Blanche of Navarre (1226 – 12 August 1283), also known as Blanche of Champagne, was the daughter of Theobald the Troubador, King of Navarre and Count of Champagne, and his second wife Agnes of Beaujeu.
She was a member of the House of Champagne.
By her marriage to John I, Duke of Brittany, she became Duchess consort of Brittany.
Blanche II of Navarre
Blanche II( 9 June 1424 – 2 December 1464), titular queen of Navarre, was the daughter of John II of Aragon and Blanche I of Navarre.
She was also Princess of Asturias by marriage.
Charles, Prince of Viana
Charles, Prince of Viana( 29 May 1421 – 23 September 1461), sometimes called Charles IV of Navarre, was the son of King John II of Aragon and Queen Blanche I of Navarre.
Isabella of Navarre, Viscountess of Rohan
Isabel d' Albret of Navarre( 1512–1555) was the daughter of John III of Navarre( died 1516) and Catherine I of Navarre, sister and heiress of Francis Phoebus, King of Navarre.
As heir apparent, her brother rose to the throne in 1517 as Henry II of Navarre, grandfather of King Henry III of Navarre( Henry IV of France).
Blanche of Navarre, Queen of France
Blanche of Navarre (1330 – 5 October 1398) was Queen of France as the wife of King Philip VI.
She was the second child and daughter of Queen Joan II of Navarre and King Philip III of Navarre.
She belonged to the House of Évreux, a cadet branch of the House of Capet, and married into the House of Valois, another cadet branch of the House of Capet.
Agnes of Beaujeu
Agnes of Beaujeu ("Agnès de Beaujeu"; ? – 11 July 1231) was a French noblewoman, the daughter of Guichard IV of Beaujeu and his wife Sybil of Hainaut.
Agnes was Countess of Champagne by her marriage to Theobald I of Navarre.
Agnes married in 1223 to Theobald.
For Theobald, this was his second marriage.
Agnes and Theobald had:
Agnes died 1231, and buried at Clairvaux.
Blanche of Navarre, Countess of Champagne
Blanche of Navarre( ?–1229) was countess and then regent of Champagne and finally also regent of her native kingdom of Navarre.
She was the youngest daughter of Sancho VI of Navarre and Sancha of Castile, who died in 1179, about two years after Blanche's birth.
Her eldest brother, Sancho VII of Navarre, succeeded their father as King of Navarre and was the last male descendant of the first dynasty of Kings of Navarre, the Pamplona dynasty, dying childless.
Her elder sister Berengaria of Navarre married Richard I of England.

Question: Who is the maternal grandfather of Blanche Of Navarre, Duchess Of Brittany?
Answer: Guichard IV of Beaujeu