GAETANI or CAETANI, the name of the oldest of the Roman princely families which played a great part in history. They are of Longobard origin, and the founder of the house is said to be Dominus Constantinus Cagetanus, who flourished in the loth century, but the family had no great importance until the election of Benedetto Gaetani to the papacy as Boniface VIII. in 1294, when they at once became the most notable in the city.
At present (in 1928) there are two lines: (1) Gaetani, princes of Teano and dukes of Sermoneta, founded by Giacobello Gae tani, whose grandson, Guglielmo Gaetani, was granted the duchy of Sermoneta by Pius III. in 1503, the marquisate of Cisterna being conferred on the family by Sixtus V. in 1585. In 1642, Francesco, the 7th duke of Sermoneta, acquired by marriage the county of Caserta, which was exchanged for the principality of Teano in 175o. The present head of the house, Onorato Gaetani, 14th duke of Sermoneta, 4th prince of Teano, duke of San Marco, marquis of Cisterna, etc., is a senator of the kingdom of Italy, and was minister for foreign affairs for a short time. (2) Gaetani dell' Aquila d'Aragona, princes of Piedimonte and dukes of Laurenzana, founded by Onorato Gaetani dell' Aquila, count of Fondi, Traetto, Alife and Morcone, lord of Piedimonte and Gioia, in 1454. The additional surname of Aragona was assumed after the marriage of Onorato Gaetani, duke of Traetto (d. 1529), with Lucrezia of Aragon, natural daughter of King Ferdinand I. of Naples. The duchy of Laurenzana, in the kingdom of Naples, was acquired by Alfonso Gaetani by his marriage in 1606 with Giulia di Ruggiero, duchess of Laurenzana. The lordship of Piedimonte was raised to a principality in 1715. The present head of the house is Nicola Gaetani dell' Aquila d'Aragona (b. 1857), 7th prince of Piedimonte and 12th duke of Laurenzana.
See A. von Reumont, Geschichte der Stadt Rom (1868) ; F. Greg orovius, Geschichte der Stadt Rom (Stuttgart, 1872), and S. A. Guar neri, Cenni storici-biografici-genealogici dei Gaetani (19o4)•