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.
Henry Bryant (naturalist)
Henry Bryant( May 12, 1820 – February 2, 1867) was an American physician and naturalist.
He was the grandfather of Henry Bryant Bigelow.
Guillaume Wittouck
Guillaume Wittouck( 1749- 1829) was a Belgian lawyer and High Magistrate.
He was the Grandfather of industrialist Paul Wittouck.
Kaya Alp
Kaya Alp was, according to Ottoman tradition, the son of Kızıl Buğa and the father of Suleyman Shah, who was, in turn, the grandfather of Ertuğrul, and the great grandfather of the Ottoman Empire founder, Osman I.
John Westley
Rev. John Westley( 1636 – 78) was an English nonconformist minister.
He was the grandfather of John Wesley( founder of Methodism).
Lyon Cohen
Lyon Cohen( 1868–1937) was a Polish- born Canadian businessman and a philanthropist.
He was the grandfather of singer/ poet Leonard Cohen.
Abd al-Muttalib
Abd al- Muttalib Shaybah ibn Hashim( c. 497 – 578) was the grandfather of Islamic prophet Muhammad.
Fujiwara no Nagara
, also known as Fujiwara no Nagayoshi, was a Japanese statesman, courtier and politician of the early Heian period.
He was the grandfather of Emperor Yōzei.
Prithvipati Shah
Prithvipati Shah( ?–1716) was the king of the Gorkha Kingdom in the Indian subcontinent, present- day Nepal.
He was the grandfather of Nara Bhupal Shah.
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.

Question: Who is the maternal grandfather of Dorotea Gonzaga?
Answer: John, Margrave of Brandenburg-Kulmbach