Complex sentence: The basilica of Santi Cosma e Damiano is one of the ancient churches of Rome called "Titulus (Roman Catholic) tituli", of which cardinals are patrons as deacons: the Cardinal Deacon of the "Titulus Ss. Cosmae et Damiani" is Giovanni Cheli.
Split into simpler sentences: The basilica of Santi Cosma e Damiano is one of the churches of Rome. The Cardinal Deacon of the "Titulus Ss. Cosmae et Damiani" is Giovanni Cheli.