Alexander of Trebizond
Alexander Komnenos or Skantarios Komnenos  was a co-emperor of the Empire of Trebizond, first with his father Alexios IV of Trebizond then, after several years in exile, with his brother John IV.
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.
Maria of Gothia
Maria of Gothia was the first wife of David of Trebizond, last Emperor of Trebizond, whom she married in 1426.
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.
Rusudan of Georgia, Empress of Trebizond
Rusudan of Georgia, Empress of Trebizond was a consort of Manuel I of Trebizond, and the mother of Empress Theodora.
Very little is known for certain about her.
Alexios IV of Trebizond
Alexios IV Megas Komnenos or Alexius IV (1382–1429), Emperor of Trebizond from 5 March 1417 to October 1429.
He was the son of Emperor Manuel III and Gulkhan-Eudokia of Georgia.
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.
Helena Kantakouzene, Empress of Trebizond
Helena Kantakouzene( died 1463) was the second wife of David of Trebizond, the last Emperor of Trebizond.
Recent research has led to doubts regarding her existence.
Irene of Trebizond
Irene of Trebizond( died around 1382) was the bigamous wife of Basil of Trebizond, by whom he had two sons, Alexios and John( later Alexios III of Trebizond), and possibly three daughters Anna, Maria and Theodora.
Hannah Arnold
Hannah Arnold, also known as Hannah Waterman King, was the grandmother of Benedict Arnolds children.

Question: Who is the paternal grandmother of Alexander Of Trebizond?
Answer: Gulkhan-Eudokia of Georgia