David of Trebizond
David Megas Komnenos (– 1 November 1463) was the last Emperor of Trebizond from 1459 to 1461.
He was the third son of Emperor Alexios IV of Trebizond and Theodora Kantakouzene.
Following the fall of Trebizond to the Ottoman Empire, he was taken captive with his family to the Ottoman capital, Constantinople, where he and his sons and nephew were executed in 1463.
In July 2013, David and his sons and nephew were canonized by the Holy Synod of the Patriarchate of Constantinople.
Their feast day was determined as 1 November, the anniversary of their deaths.
Anna of Trebizond
Anna Anachoutlou( died 1342) was Empress of Trebizond from July 17, 1341, to September 4, 1342.
Anna was the elder daughter of Emperor Alexios II of Trebizond and his Georgian wife, Djiadjak Jaqeli.
Maria of Gothia
Maria of Gothia was the first wife of David of Trebizond, last Emperor of Trebizond, whom she married in 1426.
Maria Thins
Maria Thins( c. 1593 – 27 December 1680) was the mother- in- law of Johannes Vermeer and a member of the Gouda Thins family.
Marian Shields Robinson
Marian Lois Robinson( née Shields; born July 29, 1937) is the mother of Michelle Obama, former First Lady of the United States, and Craig Robinson, a basketball executive, and the mother- in- law of former U.S. President Barack Obama.
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.
Helena Kantakouzene
Helena Kantakouzene (1333 – 10 December 1396) was the Empress consort of John V Palaiologos in the Byzantine Empire.
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.
Priscilla Pointer
Priscilla Marie Pointer( born May 18, 1924) is an American stage, film and television character actress.
She began her career in the theater, including productions on Broadway.
Later, Pointer moved to Hollywood to act in films and on television.
She is the mother of Amy Irving, therefore making her the former mother- in- law of filmmakers Steven Spielberg and Bruno Barreto and the mother- in- law of documentary filmmaker Kenneth Bowser, Jr.

Question: Who is Helena Kantakouzene, Empress Of Trebizond's mother-in-law?