Gonzalo O'Farrill y Herrera (La Habana, Cuba, 1754 – Paris, 1831) was the son of O'Farrill y Arriola, of Irish descent, and was a Spanish administrator in La Habana, Cuba. Gonzalo became (at the time of King Carlos IV of Spain), a lieutenant general of the Royal Spanish Army, Director of the Military College at Puerto de Santa María, Cadiz, Spain, and a Plenipotentiary Minister representing Spain in the Kingdom of Prussia under King Frederic. He was also a member and President of the Supreme Joint Council of Spain when King Carlos IV went to Bayonne, France to meet with Napoleon I Bonaparte around March 1808.
However, Minister of War under King Carlos IV of Spain, was for a few days later, between two spells in power of Pedro de Cevallos Guerra, (San Felices de Buelna, Cantabria, Prime Minister under King José I Bonaparte, former bonapartist King of Naples and eldest brother of Napoleon I Bonaparte.
He married a widow, who already had a child, Pedro Miguel, whose first family name was Saenz de Santamaría. Since his step son was also one of the (exiled) courtiers of ephemerous King of Naples and later Spain, José I Bonaparte, he belonged to O'Farrill's wife belonged to the Carassa family, as Pedro Miguel's second family name. His mother's single name was simply Carassa.
O'Farrill was the great uncle of Spanish-Cuban woman aristocrat Mercedes Santa Cruz y Montalvo. Mercedes Santa Cruz married around October 1809, aged 20, with French invading General Antoine Christofe Merlin, a. k. a. Merlin de Thionville, (Thionville, then in his early forties, who was Captain General of the Spanish Royal Guards two months before their wedding.
Doña Mercedes' mother, described as a sensual Cuban lady, Maria Teresa Montalvo y O'Farrill, (1771–1812), was already a widow at the age of 37. She had been in La Habana, Cuba, in 1783, and was a wife aged 12 to someone who was only 15 at the time, but was nevertheless a powerful and rich Spanish - Cuban businesswoman Joaquín de Santa Cruz y Cárdenas, (1769 - La Habana, Cuba. She died of hydropesy on a trip from Spain to Cuba, in 1807, aged 38), 3rd Conde de San Juan de Jaruco and 1st Conde de Mopox.
Maria Teresa Montalvo y O'Farrill therefore became a widow in 1807 with two very young daughters, described as the "Santa Cruz" girls. Her Literary Salon at Madrid became very popular with visitors such as the poet Manuel Jose Quintana and the famous painter Francisco de Goya.
It is said that at the time she was supposed to be the Spanish love of the new Bonaparte family King of Spain, José I Bonaparte, whose wife, Julie Clary, apparently preferred a less risky position and stayed in France with their two daughters.
When they were leaving the country in 1813 when Napoleonic troops suffered successive defeats, Mercedes Santa Cruz y Montalvo left for Paris together with his sister, María Josefa de Santa Cruz y Montalvo, who was married to another "afrancesado", Pedro Miguel Sáenz de Santa María y Carassa, the step son of General Gonzalo O'Farrill y Herrera, and a member of the State Council of the "new King" José I.
Both sisters, orphaned from "La Bella Condesa Cubana" Maria Theresa in 1812, had to leave Madrid with their great uncle Gonzalo O´Farrill, who died in Paris in 1831. In 1813. They left their respective "traitor" husbands, French General Merlin, and Don Gonzalo step son Pedro Maria Saenz de Santamaria y Carasse, in the company of the escaping group leader and ephemerous King of Spain Jose I Bonaparte. He was the former lover of her deceased mother, Maria Theresa, "La Bella Condesa Cubana".
Years later, Maria Mercedes, wife of the French General Merlin de Thionville, was used as a lover by Philarète Chasles, but earlier than that she had played hostess to French intellectuals.
Her translation into Spanish from the French of "Viaje a La Habana" had a prologue by the notorious Spanish-Cuban romantic school poet Gertrudis Gomez de Avellaneda, then living in Spain. However her hopes of getting back land, money, houses and titles confiscated by the Spanish Bourbons while she lived in exile, in particular, her appeals around 1845 to Queen Isabella II of Spain for restoration of her titles and properties did not lead anywhere.