This particular Peter Grandados had a sister Nellie. Not sure if it is any connection to your grandparents. Also found a reference to your parents marriage. His birth and death information indicate his mother's last name was Rivera?
U S Census, 1940 Councilmanic District 13, Los Angeles, CA
Citing this Record: "United States Census, 1940," index and images, FamilySearch (https://familysearch.org/pal:/MM9.1.1/K9H5-DZH
Head Pedro Granados M 50 CA
Wife Manuela Granados F 40 CA
Dau Nellie Granados F 13 CA
Dau Elizabeth Granados F 11 CA
Son Pedro Granados M 9 CA
Son Radolpho Granados M 7 CA
Son Margareto Granados M 4 CA
Son Daniel Granados M 1 CA
California, County Marriages, 1850-1952
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IMAGE SOURCE: https://familysearch.org/pal:/MM9.3.1/TH-1971-29892-20827-99?cc=1804002
Name: Peter Granados Jr
Marriage 24 Oct 1954 Los Angeles, CA
White Male Single Age: 23 Birth (Est) 1931
Father Pedro D Granados Birth Mexico
Mother Manuela Munoz Birth Mexico
Spouse Gloria Jean Gardetto
Female Age: 22 Birth (Est): 1932
Father Joe Gardetto Birth CA
Mother Nina Peluffo Birth CA
Nevada, Marriage Index, 1956-2005
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Name: Peter Granados
Marriage 17 Sep 1977 Clark, NE
Residence Place: California
Registration : 22 Sep 1977 Place: , Clark, Nevada
Spouse Pamela Christin Praxmarer
Residence Place: California
Type of Officiator: Religious celebrant
Page: B110792 Book Number: 521
Instrument Number: 907863
Registration Year (Original): 1977
California, Death Index, 1940-1997
Citing this Record "California, Death Index, 1940-1997," index, FamilySearch (https://familysearch.org/pal:/MM9.1.1/VGGB-T3Q
Name: Peter Granados Male
Death 18 Jul 1984 Los Angeles, CA
Birth Date: 08 May 1959 California
Mother Rivera
California, Birth Index, 1905-1995
Citing this Record "California, Birth Index, 1905-1995," index, FamilySearch (https://familysearch.org/pal:/MM9.1.1/VGSR-HTX
Name: Peter Granados Male
Birth 08 May 1959 Los Angeles, CA
Mother: Rivera