What bank was founded by the great-great-great grandfather of the second Duke of Florence?
Giovanni di Bicci de' Medici: 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. Giovanni di Bicci de' Medici:  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. Cosimo I de' Medici, Grand Duke of Tuscany: 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.
the Medici Bank