[1] Born in Florence, he was the son of Cosimo I de' Medici, Grand Duke of Tuscany, and Eleanor of Toledo.

In 1562, he accompanied his father and brothers Giovanni and Ferdinando, to the Tuscan coast to embark to Spain, where the eldest son Francesco lived.

But his mother Eleanor and the children contracted malaria, and all except Ferdinando died in a few weeks.

Centuries after his death, a myth arose saying that Garzia had murdered his brother, Giovanni, following a dispute in 1562.

However, modern exhumations showed no signs of violence on the bodies and they were found to have died together of malaria in 1562.