George Windsor, Earl of St Andrews
George Philip Nicholas Windsor, Earl of St Andrews (born 26 June 1962) is the elder son of Prince Edward, Duke of Kent, and his wife Katharine, Duchess of Kent.
He is styled Earl of St Andrews, one of his father's subsidiary titles, which he holds by courtesy as heir apparent to the Dukedom of Kent.
Edward Windsor, Lord Downpatrick
Edward Edmund Maximilian George Windsor, Lord Downpatrick (born 2 December 1988), known professionally as Eddy Downpatrick, is an English fashion designer and former financial analyst.
He is the co-founder and creative director of the British fashion label FIDIR.
Lord Downpatrick is a relative of the British royal family.
As second-in-line to the Dukedom of Kent, he uses one of his grandfather's subsidiary titles, Baron Downpatrick, by courtesy.
He is the most senior member of the royal family to be excluded from the line of succession for being Catholic.
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.
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.
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.
Hannah Arnold
Hannah Arnold, also known as Hannah Waterman King, was the grandmother of Benedict Arnolds children.
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.
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.
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.
Edward Windsor, 3rd Baron Windsor
Edward Windsor, 3rd Baron Windsor (1532 – 24 January 1574) was an English peer.

Question: Who is Edward Windsor, Lord Downpatrick's paternal grandmother?
Answer: Katharine, Duchess of Kent