Her first marriage was to Rafael Márquez y Osorio, 7th Count of the Torres de Alcorin, in 1977, and she has a child with him. Her second marriage is to Tomás de Terry y Merello in 1990. She has another child by this marriage. The third child of Luisa Isabel is Gabriel Ernesto González de Gregorio y Alvarez de Toledo, born in 1958. She and her husband lived separately since 1958 and were officially divorced in 2005. Eleven hours before her death, 7 March 2008, Luisa Isabel married her longtime partner and secretary since 1983, Liliana Maria Dahlmann in a civil ceremony on her deathbed. Today, the Dowager Duchess Liliana Maria, her legal widow, serves as life-president of the Fundación Casa Medina Sidonia. Luisa Isabel Alvarez de Toledo was the head of the House of Medina Sidonia, the most important ducal house of Spain, with its status as a hereditary title having been granted in 1445. The principal residence of the dukes was the Palace of Medina Sidonia, located in Sanlúcar de Barrameda, Cádiz. This Palace houses the "Archivo de la Casa de Medina Sidonia", one of the most important private archives in Europe. An atypical and controversial aristocrat, she was a historian, the guardian of the ducal archives and the author of numerous works. At the age of 18, she was presented to society in Estoril, Portugal, along with the Infanta Pilar de Borbón. Yet, despite her aristocratic heritage and upbringing, she held strong socialist ideals throughout her life. She is said to have been a member of the then illegal Spanish Socialist Workers' Party (PSOE). Her anti-Francoist activities brought about her incarceration in the prison of Alcalá de Henares during the 1960s. It was from this time that she became popularly known as the "Red Duchess." She established and, until her death, was an active president of the Fundación Casa Medina Sidonia that manages the "Archivo de la Casa de Medina Sidonia", the major part of the patrimony of the House of Medina Sidonia, and she continued her work as an historian and author. During her extensive research in the archives she discovered documents which convinced her that America might have been discovered a long time before Columbus by Arab-andalusian or Moroccan sailors trading with ports in Brazil, Guayana and Venezuela and she published her views in "No fuimos nosotros" ("It wasn't us") and "África versus América".