Galileo's son who was later legitimized as his heir was Vincenzo.
Vincenzo was born in Padua in 1606 to Galileo and Marina Gamba, who were not married. Galileo and Marina also had two daughters, Virginia and Livia. Because their births were illegitimate under the law of the time, the girls later entered religious life rather than marrying.
After Marina's death, Vincenzo's status was regularized. In 1619, the Grand Duke of Tuscany legitimized him, allowing him to become Galileo's legal heir. He later married Sestilia Bocchineri and took a strong interest in music and mechanics, following the family connection to the lute.
Vincenzo is sometimes confused with his grandfather, also named Vincenzo Galilei, a noted musician and music theorist. Galileo's son also helped his father during Galileo's final years, including work on an escapement mechanism. He died in 1649, several years after Galileo.