Cosimo de' Medici was born in Florence to Giovanni di Bicci de' Medici and his wife Piccarda Bueri on 10 April 1389. At the time, it was customary to indicate the name of one's father in one's name for the purpose of distinguishing the identities of two like-named individuals; thus, Giovanni was the son of Bicci, and Cosimo's name was properly rendered Cosimo di Giovanni de' Medici. He was born along with a twin brother Damiano, who survived only a short time. The twins were named after Saints Cosmas and Damian, whose feast day was then celebrated on 27 September; Cosimo would later celebrate his own birthday on that day, his "name day", rather than on the actual date of his birth. Cosimo also had a brother Lorenzo, known as "Lorenzo the Elder", who was some six years his junior and participated in the family's banking enterprise.