Born in Venice of the aristocratic del Monte family of Tuscan origin (which provided several cardinals to the Church), he was the son of Marquis Ranieri Bourbon del Monte, first count of Monte Baroccio, and Minerva Pianosa. He began his ecclesiastical career as Abbot commendatario of Santa Croce a Monte Fabali. He then went to Rome when he was still quite young, and was appointed as auditor for Cardinal Alessandro Sforza, before being finally admitted into the court of Cardinal Ferdinando de' Medici. He made his way up through the clerical ranks as Referendary of the Tribunals of the Apostolic Signature of Justice and of Grace (1580), and later went to serve the grand-duke of Tuscany, the former Cardinal Ferdinando de' Medici.