Kilab ibn Murrah (Arabic: كلاب بن مُرة‎ ‎ ) (born 373 CE) was the paternal great-great-great-great grandfather and maternal great-great-great grandfather of the Islamic prophet Muḥammad.
Giovanni di Bicci de' Medici (c. 1360 – February 20/28, 1429) was an Italian banker, a member of Medici family of Florence, and the founder of the Medici Bank.
 While other family members, such as Chiarissimo di Giambuono de' Medici, who served in the Signoria in 1201, and Salvestro de' Medici, who was implicated in the Ciompi Revolt of 1378, are historically significant, Giovanni's founding of the family bank truly began the family's rise to power in Florence.
 He was the father of Cosimo de' Medici ("Pater Patriae"), grandfather of Piero di Cosimo de' Medici, great-grandfather of Lorenzo de' Medici (the Magnificent) and great-great-great-grandfather of Cosimo I de' Medici, Grand Duke of Tuscany.
Benjamin Harrison III (1673 – April 10, 1710) was an American Virginia politician.
 He was an early member of the Harrison Family of Virginia, serving as the colony's Attorney General, Treasurer, and Speaker of the House of Burgesses.
 He was the great grandfather of 9th U.S. President, William Henry Harrison and the great-great-great grandfather of 23rd U.S. President, Benjamin Harrison.
The Horn Papers were a genealogical hoax consisting of forged historical records pertaining to the northeastern United States for the period from 1765 to 1795.
 They were published by William F. Horn of Topeka, Kansas between 1933 and 1936, and presented as a transcription of documents of his great-great-great grandfather, Jacob Horn (died 1778), and other members of the Horn family.
George Spencer, 4th Duke of Marlborough, (26 January 1739 – 29 January 1817), styled Marquess of Blandford until 1758, was a British courtier, nobleman, and politician from the Spencer family.
 He served as Lord Chamberlain between 1762 and 1763 and as Lord Privy Seal between 1763 and 1765.
 He is the great-great-great grandfather of Sir Winston Churchill.
Cosimo I de' Medici (12 June 1519 – 21 April 1574) was the second Duke of Florence from 1537 until 1569, when he became the first Grand Duke of Tuscany.
Shebuel (Hebrew: שבואל‎ ‎ ) was a descendant of Gershom, the son of Moses and Zipporah.
 He, along with his kinsman Rehabiah a descendant of Eliezer, were described as chiefs and included in the Tribe of Levi.
 Shebuel is also described as "ruler of the treasures".
 His name means "captive of God" or "returned of God".
 His patrilineal lineage can be traced back to Abraham, Isaac, and Jacob since Levi is both his great-great grandfather (through Jochebed) and great-great-great grandfather (through Amram).
 He is also descended from Jethro and Jethro's ancestor Midian, son of Abraham and his second wife Keturah, through his paternal grandmother Zipporah.
Sir William Pepperrell, 1st Baronet (27 June 1696 – 6 July 1759) was a merchant and soldier in Colonial Massachusetts.
 He is widely remembered for organizing, financing, and leading the 1745 expedition that captured the French garrison at Fortress Louisbourg during King George's War.
 During his day Pepperrell was called "the hero of Louisburg," a victory celebrated in the name of Louisburg Square in Boston's Beacon Hill neighborhood.
 He is the great-great-great grandfather of actor Robert Hardy.
Adam Hawkes (January 25 or 26, 1605 - March 13, 1672) was an English immigrant who was the original settler of what is now known as Saugus, Massachusetts, United States.
 He is also great-great-great grandfather of second President of the United States John Adams.
The People of Juvik is a series of six historical novels by Norwegian author Olav Duun.
 The books chronicle the lives of the Juvikings, an old Norwegian landowning peasant family living in the Namdal valley.
 The series covers six or seven generations of Juvikings, starting with Per Anders Juvika, the last of the old style Juvikings, and ending with Per and Anders, the sons of Odin Setran, Per Anders' great-great-great grandfather.
 The first novel, "The Trough of the Wave" ("Juvikingar" in Norwegian), starts out at Juvik, a fictional farm in the Namdal, but moves to Haaberg when Per Anders' son Per leaves his ancestral lands and buys his sister's late husband's farm.
 The first three books follow the Juvikings from the 18th century to the late 19th; the final three follow the childhood, life and eventually death of Odin.

Question: What bank was founded by the great-great-great grandfather of the second Duke of Florence?
Answer: the Medici Bank