Antonio Foscarini had two brothers, Alvise (1560–1617) and Girolamo (1561–1580), and three sisters, Caterina, Agnesina, and Luca Contarini. The Foscarini family lost a substantial part of their wealth, from the Ottoman–Venetian War (1570–1573) and only the sons received financial support. His father Nicolò died in 1575, and his mother died in 1582, probably by suicide.