I found the birth record for Francisco Raul Ortiz; apparently his mother was not married at the time of his birth. Here is the citation for that record:
"El Salvador Registro Civil, 1704-2001," database with images, FamilySearch(https://www.familysearch.org/ark:/61903/1:1:QLS6-SPJK : 15 April 2022), Francisco Raúl Ortíz, ; citing , Birth Registration; citing , departmento de la Libertad, Registros Civiles (Department of Libertad, Civil Registers), El Salvador; FHL microfilm 1,159,158. Image 61 of 677.
This is the birth record for the sister:
"El Salvador Registro Civil, 1704-2001," database with images, FamilySearch(https://www.familysearch.org/ark:/61903/1:1:Q26Z-RMCN : 15 April 2022), Domitila de Jesus Ortiz, ; citing , Birth Registration; citing , departmento de la Libertad, Registros Civiles (Department of Libertad, Civil Registers), El Salvador; FHL microfilm 1,159,156.
Neither record says much about the mother.
Were the children in the family baptized? Contacting the church might yield their baptismal records. Sometimes records for children of unmarried parents will name both parents. Also, some Catholic baptismal records name the grandparents.
Sometimes when you write to the Church your letter is just ignored, and you never get a reply. You would probably have a better chance of success if somebody personally went to the church.
