Originally named Scipione Caffarelli, he was born in Rome, the son of Francisco Caffarelli and Ortensia Borghese. His father ran into financial difficulties, so Scipione's education was paid for by his maternal uncle Camillo Borghese. Upon Camillo's election to the papacy as Pope Paul V in 1605, he quickly conferred a cardinalship on Scipione and gave him the right to use the Borghese name and coat of arms.