This is the only record I could find for this name in Riverside County. The birth year is off by 3 yrs. It's from the Ca Death Index and the mother's maiden name is probably the adoptive mom. I don't know if they even have any adoption records going back that far. Check with the State first to see if they have any suggestions on your next step.
Marion G Castillo
Social Security #:554096913
Sex:Male
Birth Date: 23 Apr 1886
Birthplace:California
Death Date:17 Oct 1963
Death Place:Riverside
Mother's Maiden Name:Lujan