Giovanni was the second son of Cosimo 'il Veccio' and his wife Contessina de Bardi, he was born on 3 June 1421 in Florence. He had all the family love of learning, and many manuscript books collected by him are still in the Medici library in San Lorenzo. As the chronic ill-health of his elder brother Piero made it unlikely that the latter would survive their father, Giovanni was brought up as the future head of the family, was looked on by all as his father's successor, and was Cosimo's favorite son. To a family situated as the Medici were at this time, it was of utmost importance that whoever succeeded Cosimo as the head of the house should be both capable and popular, and Giovanni did not come short of his father's hopes in this respect. His ability, good sense, tact and knowledge of people made him highly popular, and he promised to be a worthy successor of Cosimo. So as Piero's health grew from year to year worse, all the hopes of the family rested on Giovanni. He was married to Ginevra degli Albizzi, one of that 
family who so violently opposed Cosimo in his earlier years and tried to organize his ruin and death. Giovanni and Ginevra's only child, a son, then nine years old, died in 1461.
But, alas, in 1463, Giovanni, the hope of the house, died. The grief into which the family was plunged was very great. Cosimo was broken down, physically helpless, and his death soon to be expected; Piero was likely to die any day; and his eldest son, Lorenzo, was only fourteen years old. So that with Giovanni dead it seemed that all the prospects of the family were destroyed; for it was well known that powerful enemies (including all those other families in Florence jealous of the one which was rising to such eminence) were on the watch for an opportunity to bring its power to an end.
Giovanni was buried in the family church of San Lorenzo, which was then just finished by his father. Giovanni di Bicci and Picarda Bueri, had already been buried in the sacristy, and their grandson, this second Giovanni, was now also interred there. And when six years later his brother Piero died, the sculptor Veroccio, Donatello's best pupil, was called upon to design a joint tomb for the two brothers, and executed a very tasteful one, which is considered his earliest important work.

Source: Artem Kaplan