He was the eldest son of Ugo, 4th Duke of Sora and Duchess Maria Ruffo di Bagnara.

He married Giustina Gallio (29 October 1644 – 21 July 1679) and then, when she died, he married Ippolita Ludovisi on 19 October 1681.^[1] The Boncompagni-Ludovisi union lasted until the French Revolution and included the development of the Archivio Boncompagni-Ludovisi held by The Vatican.^[2]

Gregorio and Ippolita had six children:

Hugo (1684–1686) died young
Maria Eleonora (1686–1745), Princess of Piombino, married her uncle and Gregorio's brother Antonio I Boncompagni
Constance (1687–1768), married Vincenzo Giustiniani, Prince of Bassano
Maria Teresa (1692–1744), married Urbano Barberini, Prince of Palestrina
Giulia (1695–1751), married Marco Ottoboni, Duke of Fiano
Anna Maria (1696–1752), married Gian Vincenzo Salviati, Duke of Giuliano

Biography

References