In 1616 he secretly married Camilla Faà di Bruno, whom he divorced in the same year. Their son Francesco Giacinto Teodoro Giovanni Gonzaga, although accepted at court, was not made Ferdinando's heir. He died of the plague during the 1630 siege of Mantua. On 16 February 1617 he married Catherine de' Medici (1593–1629), the daughter of Ferdinand I, Grand Duke of Tuscany.