Rondinini was born in 1617 to Alessandro Rondinini and Felice Zacchia. He was the grandson of Cardinal
Laudivio Zacchia (who had been married and had two children including Felice Zacchia before accepting an ecclesiastic career) and was the grand-nephew (also on his mother's side) of Cardinal
Paolo Emilio Zacchia. He studied at the
University of Perugia and then became a clerk of the
Apostolic Chamber in 1637 at age 20. During the
First War of Castro he endeared himself to the
Barberini and their uncle
Pope Urban VIII by raising his own
company of
cuirassiers to fight on the side of papal forces. ==Cardinalate==