Personal life
On 28 May 1875 in Madrid, he married María de la Asunción Caro y Széchényi (1853–1897), a daughter of Pedro Caro y Álvarez de Toledo, 5th Marquis of La Romana, and Countess Erzsebet "Elisabeth" Széchényi (a granddaughter of Count Ferenc Széchényi). Her brother, Pedro Caro y Széchényi, 6th Marquis of La Romana, married Don Carlos' sister, María de la Piedad. Before her death on 7 September 1897, they were the parents of eleven children, four of whom died at an early age, including:
Carlos Martínez de Irujo y Caro (1877–1906), who became the 4th Marquis of Casa Irujo in 1904, but predeceased his father in 1906.
Asunción Isabel Martinez de Irujo y Caro (1879–1964), who married Cristóbal García-Loygorri, 3rd Duke of Vistahermosa, son of Narciso García-Loygorri, 2nd Duke of Vistahermosa.
María de la Piedad Martinez de Irujo y Caro (1880–1954)
María del Rosario Martinez de Irujo y Caro (1881–1951), who married Manuel de Mendívil y Elío, the Governor of Spanish Guinea in 1937.
Pedro Martinez de Irujo y Caro, 9th Duke of Sotomayor (1882–1957), who married Ana María de Artázcoz y Labayen, a daughter of Francisco Javier Artázcoz y Urdinola.
Juan Guaberto Martinez de Irujo y Caro (1883–1892), who died young.
Luis Martinez de Irujo y Caro (1886–1962), who married Guadalupe Aspe y Suinaga.
Teresa Martinez de Irujo y Caro (1888–1892), who died young.
Gabriela Martinez de Irujo y Caro (1890–1892), who died young.
Cristina Martinez de Irujo y Caro (1892–1986), who married Emilio Aznar y de la Puente, 2nd Marquis of Zuya.
Fernanda Martinez de Irujo y Caro (1895–1901), who died young.
On 11 March 1899, he married María del Pilar Caro y Széchényi (1864–1931), younger sister of his first wife and widow of the Marquis of San Felices, José María Guillamas y Piñeiro, Grandee of Spain, who died in 1895. Together, they were the parents of three children, including:
María del Carmen Martínez de Irujo y Caro (b. 1899), who married Alejandro Pidal y Guilhou, son of Pedro Pidal, 1st Marquis of Villaviciosa de Asturias.
Carlota Martínez de Irujo y Caro (1904–1945), who married Gonzalo Taboada y Sangro, a son of Carlos Taboada y Bugallo and María Victoria Sangro y Ros de Olano, 3rd Countess of Almina.
The Duke died on 14 September 1909 at San Sebastián. After his death, his widow, María del Pilar, remarried for the third time to the 12th Marquis of Martorell on 24 March 1922.
