González de Gregorio married firstly his distant cousin María Montserrat Viñamata y Martorell, younger daughter of Luis Viñamata y Emmanueli and The Countess of Alba de Liste, on 12 December 1983, and divorced in 1998. They had two children:
Don Alonso Enrique González de Gregorio y Viñamata, 14th Duke of Fernandina (b. 1983)
Doña María de la Soledad González de Gregorio y Viñamata (b. 1989), who married in September 2017 Jérémy Bégard.
The Duke married secondly Pamela García Damián, of Venezuelan origin, daughter of Armando García Liceaga y Pérez de Viñaspre and María Pilar Damián Gracia, in 2001.
Ancestry
Ancestors of Leoncio Alonso González de Gregorio, 22nd Duke of Medina Sidonia
16. Pedro González de Gregorio y López-Montenegro
8. Leoncio González de Gregorio y Martínez de Azagra
17. Micaela Martínez de Azagra y Garcés de Marcilla
^Although with the Countship of Niebla not a Grandeeship of Spain is attached, the Duke was styled already as The Most Excellent, since he was heir apparent to a Grandee, who are styled similar as their parents (while younger children are styled The Most Illustrious). Francisco López-Nieto y Mallo, Honores y Protocolo, 2 Volumes, Consultor, 2006. ISBN84-7052-290-6 and ISBN978-84-7052-290-1