The Caetani, or Gaetani family has Roman and Gothic origins. According to family tradition they were descendants of the Dukes of Gaeta, and traced their maternal ancestry to the Roman gens Anicia through the Counts of Tusculum. The founder of the house was Marinus I, Duke of Fondi, son of Docibilis II of Gaeta, from which the family gets its name. His successor was Constantine, who took the name "Cagetanus" and ruled in the latter half of the 10th century. In the late eleventh century, a descendant of his, Crescentius, was duke. This Crescentius was the father of two illustrious people: his successor, Marinus, and his son John (called "Gaetanus" or "Coniulo") from Pisa, who was Pope Gelasius II. Marinus was succeeded by his son Crescentius, who defended his uncle the pope resolutely from imperialist attacks.