Gianfrancesco Gonzaga (1446–1496)
Gianfrancesco Gonzaga (1446 - 28 August 1496) was the third son of Ludovico III Gonzaga, Marquess of Mantua and Barbara of Brandenburg.
He was the first count of Sabbioneta from 1479 until his death, originating the Gonzaga-Sabbioneta line.
Carlo Gonzaga of Milan
Carlo Gonzaga( died 21 December 1456), Lord of Sabbioneta, was an Italian nobleman of the Mantuan House of Gonzaga who rose to the position of Captain of the People in the Ambrosian Republic of Milan, and eventually ruled practically as an autocrat.
He was the younger son of Gianfrancesco Gonzaga and Paola Malatesta, as well as a friend of the humanist writer Francesco Filelfo.
His brother was the famous Ludovico III Gonzaga, Marquis of Mantua, and became a rival of his for Mantua and in the field of battle.
Barbara of Brandenburg, Marquise of Mantua
Barbara of Brandenburg (1422 – 7 November 1481) was a Marchioness consort of Mantua, married in 1433 to Ludovico III Gonzaga, Marquis of Mantua.
Barbara was the daughter of John, Margrave of Brandenburg-Kulmbach, and Barbara of Saxe-Wittenberg and a niece of Holy Roman Emperor Sigismund.
Her marriage took place in 1433, when she was only ten years old, and she spent the latter part of her childhood in Mantua.
She was active as the political adviser of her spouse with the responsibility of foreign diplomatic correspondence, in particular when it pertained to relations between Mantua and Germany.
She is regarded as an important figure in the Italian Renaissance and was a student of Vittorino da Feltre.
Barbara is portrayed in the novel "The Princess of Mantua" by French writer Marie Ferranti.
Mona Hopton Bell
Mona Hopton Bell( 1867- 1940) was a British artist, best known for her portraits of civic figures.
She was the grandmother of the painter Jean H. Bell.
Diana Guardato
Diana Guardato was a member of the aristocratic Patrician Guardato family, and had three children with King Ferdinand I: Diana Guardato is the 16th- Great Grandmother of His Royal Highness Albert II of Belgium, 15th- Great Grandmother of His Majesty Juan Carlos
I of Spain, 17th- Great Grandmother of Philippe of Belgium, 14th- Great Grandmother of His Majesty Manuel II of Portugal, 16th- Great Grandmother of Grand Duke Henri, as well as many others.
Hubba bint Hulail
Hubba bint Hulail was the grandmother of Hashim ibn' Abd Manaf, thus the great- great- great- grandmother of the Islamic" Nabī"( Prophet) Muhammad ibn Abdullah.
Hannah Arnold
Hannah Arnold, also known as Hannah Waterman King, was the grandmother of Benedict Arnolds children.
Tjuyu
Tjuyu( sometimes transliterated as Thuya or Thuyu) was an Egyptian noblewoman and the mother of queen Tiye, and the wife of Yuya.
She is the grandmother of Akhenaten, and great grandmother of Tutankhamun.
Anne Denman
Anne Denman( 1587–1661) was born in Olde Hall, Retford, Nottinghamshire.
Through a fortunate second marriage with Thomas Aylesbury, she became the grandmother of Lady Anne Hyde, Duchess of York and great- grandmother of Queen Mary II and Queen Anne.
Kaoru Hatoyama
After the elections of 2009, she became more widely known as the grandmother of Prime Minister Yukio Hatoyama and his politician brother Kunio Hatoyama.

Question: Who is Gianfrancesco Gonzaga (1446–1496)'s maternal grandmother?
Answer: Barbara of Saxe-Wittenberg