Boncompagni family.

The house of Boncompagni had its origin in Umbria but moved to Bologna in the thirteenth century where the family was comfortable but not wealthy. Many of their descendants were members of the armed forces. The foundations of its fortune were laid by Cardinal Ugo Boncompagni who was elected pope in 1572 under the name of Gregory XIII.

From this pontiff, whose name was immortalized by his reformation of the calendar, the family is directly descended through a natural son of Gregory's named Giacomo who married a Sforza di Santa Fiora. Gregory gave Giacomo the titles duke of Sora and d'Arpino and marquis of Vignola and enriched him accordingly. Perhaps no other family enjoyed the fruits of nepotism to the extent of the Boncompagni. Through carefully arranged alliances with the heiresses of three other papal families, the Boncampagni were able to accumulate significant wealth.

Giacomo married Ippolita Ludovisi who brought as her dowry the great wealth of Gregory XV (Ludovisi) while the pope's brother Niccolo by three marriages accumulated immense riches in his house. Niccolo's first wife, Isabella Gesualdi, brought with her the princedom of Venosa. His second wife was a Mendoza who brought him the principality of Piombino with almost sovereign sway over that small state. The third was Constance Pamphili, daughter of the notorious Olimpia Maldaichini, sister-in-law of Innocent X (Pamphili) who had great influence over the pope and in Rome.

The state of Piombino, already mentioned as having been acquired through the Mendoza marriage, had been inherited by that family from the d'Arpini, originally a peasant family, but with ambitions "above the plow" that raised them in 1392 to the condition of independent rulers. Their authority was transmitted to their descendants of the other houses already mentioned.

The principate of Piombino remained with the Boncompagni up to the Napoleonic invasion. They did not return the patrimonial rights until the Congress of Vienna (1815) with the conclusion of a settlement in money from part of the grand duchy of Tuscany in which Piombino was incorporated. In the eighteenth century Pietro Gregorio Boncompagno married Maria Francesca, last of the Ottoboni family, adding her name to the line. By remaining faithful to Spain the Boncompagni did not play an important part in the political policies of their time.

Notwithstanding its former great wealth the Boncampagni family became comparatively poor. Its once famous estate within the walls of Rome was divided into innumerable villas, and the great though modern palace of the family was taken over as a residence for the queen mother. The precise relationship between the series listed below and the family was not determined.