Descended from Boncompagno, who with his brothers Paolo and Federico joined the First Crusade in 1097; Rodolfo, son of Boncompagno, was Lord of Assisi in 1133, and ancestor of Rinaldo, Duke of Spoleto, and Nicoḷ, Bishop of Assisi (1304). Resident in Visso 1133 and Bologna by 1243. Bante and Apollonio were cr Counts of Rocca Macereto (Visse) 2 May 1401 by Pope Boniface IX. Cristoforo, m to Angela Marescalchi, was father of Ugo (b 1502) elected Pope Gregory XIII (1572-1585). His legitimated son Jacopo, Marquess of Vignola (1578), Duke of Sora (1580), Duke of Arce (1583), Patrician of Venice (1573), Lord of Arpino, Aquino, Roccasecca etc., m Costanza Sforza, dau of Sforza Sforza Sovereign Count of S. Fiora. Gregorio II Boncompagni, Duke of Sora and Arce, Marquess of Vignola etc. (1642-1707) m 1681 Ippolita Ludovisi, heiress of the Ludovisi family and of the Sovereign Principality of Piombino, and the Lordship of the island of Elba (by matrimonial pact the descendants all have the name Boncompagni Ludovisi). [Elba, Piombino and Populonia, acquired by the family of Appiani 1399; Piombino and Elba erected into an immediate fief of the Empire 8 Nov 1509, this fief inherited by Nicoḷ Ludovisi by right of his wife Polyxena Mendoza, dau of Isabella Appiani, invested by the Emperor 24 Mar 1634 (against a payment of 1,050,000 florins), and confirmed by Imperial Patent 21 Apr 1634, and 8 Nov 1638, with the Marquesate of Populonia, and of the titles Prince of Venosa (inherited from the Gesualdi family 16 May 1658), Count of Conza etc. great-niece of Alessandro Ludovisi, elected Pope Gregory XV (1621-1623).] The right of sub-investiture of Piombino granted to the King of Spain 1713, who ceded this right to the King of Naples 1736 (with the obligation to return this right to the Emperor). Gaetano Boncompagni-Ludovisi, 3rd Prince of Piombino and of the H.R.E. was cr Grandee of Spain (attached to title of Prince of Piombino) 18 Oct 1739, and Grandee of Spain attached to the Dukedom of Sora 18 Mar 1739 & 24 Mar 1777; used the title of Serene Highness. Sovereignty of Piombino and Elba lost in 1797, ceded by the King of Naples to the Kingdom of Etruria 28 Mar 1801, later incorporated into the Grand Duchy of Tuscany invested on Elisa Bonaparte. Piombino returned to Principe Luigi Boncompagni Ludovisi by the Congress of Vienna 1815 but subsequently ceded to the Grand Duke of Tuscany. The Congress of Vienna (art. 100 of the final Act) reserved for him and his heirs the title of Prince of Piombino. Duke of Monterotondo, Rome 1814, Roman Prince and Noble of Rome coscritto 1854; Don and Donna for all descendants. Titles of Prince of the HRE (primog) and Prince and Princess for all descendants (mf), Prince of Piombino (mpg), Duke of Sora and of Arce, Duke of Monterotondo, Marquess of Populonia, Marquess of Vignola and Count of Conza (all mpg), Patrician fo Venice (mf), Noble of Rome (mf), Coscritto (primog), Noble and Patrician of Naples (m), Patrician of Ravenna (m), Patrician of Bologna (m), Patrician of Orvieto (mf), Noble of Jesi (mf), recognized by the Kingdom of Italy, 7 Mar 1900, Noble of Rieti (mf) recog Italy 3 Mar 1901, Prince of Venosa (mpg), recog 31 May 1931.