Gülbahar Hatun (wife of Mehmed II)
Gülbahar Hatun( 1432 – 1492) was the consort of Sultan Mehmed II, and mother of Sultan Bayezid II of the Ottoman Empire and the grandmother of Selim I.
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.
Dorotea Gonzaga
Dorotea Gonzaga (6 December 1449 – 20 April 1467) was a Duchess Consort of Milan.
She was the daughter of Ludovico III Gonzaga, Marquess of Mantua and Barbara of Brandenburg.
In 1466, Dorotea married Galeazzo Maria Sforza, but she died in 1468.
Her husband was remarried to Bona of Savoy.
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.
Hüma Hatun
Hüma Hatun (1410 ‒ September 1449) was the fourth wife of Ottoman Sultan Murad II and mother of Mehmed II and the grandmother of Bayezid II.
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.
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.
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.
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.

Question: Who is Dorotea Gonzaga's maternal grandmother?
Answer: Barbara of Saxe-Wittenberg