Fernando Martínez de Sotomayor was the son of Antonio Martínez de Sotomayor and María Valenzuela according to his dispensa - https://familysearch.org/pal:/MM9.3.1/TH-1-18413-9191-35?cc=1874591&wc=…

Fernando's brother, Joseph Antonio, also had a dispensa which mentions in more detail their ancestors -
https://familysearch.org/pal:/MM9.3.1/TH-1-18410-40916-67?cc=1874591

Antonio Martínez de Sotomayor was the son of Andrés Martín de Sotomayor y González who married Beatriz de Mayorga 13 June 1666 in Aguascalientes. She was the daughter of Alvaro Marín de Peñaloza and Isabel de Mayorga
https://familysearch.org/pal:/MM9.3.1/TH-266-12446-30193-28?cc=1502404&…

Andrés Martín de Sotomayor y González was the son of Andrés Martín de Sotomayor and María González de Islas y Moctezuma.

Andrés Martín de Sotomayor was the son of Andrés Martín Camacho and María de las Ruelas o Sotomayor.

Alvaro Marín de Peñaloza was the son of Juan Marín de Peñaloza and María de Sandi.

María de Sandi was the daughter of Álvaro Carrillo and María Álvarez de Sandi

Alvaro Marín de Peñaloza and Isabel de Mayorga had a daughter named Isabel de Mayorga that married Gabriel López de Nava y González de Ruvalcaba 18 may 1657 in Aguascalientes.
https://familysearch.org/pal:/MM9.3.1/TH-267-11824-50419-18?cc=1410092

Gabriel López and Isabel de Mayorga had Gabriel López who married Nicolasa Petronila Valenzuela and they had Isabel Rosaura López the wife of Joseph Miguel Romo de Vivar and, in a second marriage, of Joseph Antonio Martínez de Sotomayor y Valenzuela.

That same Isabel Rosaura López was the mother of Isabel Gertrudis Romo de Vivar, the wife of Fernando Martinez de Sotomayor y Valenzuela.

Armando