A member of the Aldobrandini family, Giovanni Aldobrandini was born in 1525, probably in Florence.[1] He was the son of Silvestro Aldobrandini, governor of Fano, and wife Lisa Donati. His father was banished from Florence for opposing the Medici.
His siblings were Cardinal Ippolito Aldobrandini (1536–1605), who became Pope Clement VIII in 1592, Pietro Aldobrandini (? - Rome, 11 February 1587), married to Flaminia Ferracci (? - Rome, 27 April 1603), sister of lawyer Muzio Ferracci (parents of Olimpia Aldobrandini, 1st Princess of Rossano, and Cardinal Pietro Aldobrandini), Bernardo Aldobrandini, married to Livia Capizucchi, Giulia Aldobrandini, married to Aurelio Personeni da Ca' Passero (parents of Cinzio Personeni da Ca' Passero (Senigallia, 1531 - Rome, 1 January 1610)), and Elisabetta Aldobrandini, married to Aurelio Passeri, Doctor in Fine Arts and Medicine, son of Bernardino Passeri and wife (parents of Cardinal Cinzio Passeri Aldobrandini).[2]