You didn't give much information on this couple in your query so I took a look at your message history. You gave more on the Seigler Forum, and you received a good reply. You didn't mention the name was spelled differently on the 1900 census, that can help. Here's a reply to you query there.
There is a John M. "Seaglar" family in the 1900 census of ED 64 Justice Precinct 1 (excl. Cameron city), Milam, Texas, that appears to match your criteria, except for the dates: Household Gender Age Birthplace Head John M Seagler M 45 South Carolina, married 14 years Wife Francis J Seagler F 31 South Carolina Son Charlie W Seagler M 9 South Carolina Son John G Seagler M 5 South Carolina Daughter Pearl S Seagler F 4 South Carolina Daughter Ada D Seagler F 2 South Carolina The 1900 census record for this family is here: https://familysearch.org/pal:/MM9.1.1/M3PN-DB7
They appear 20 years later in the 1920 census of Comanche, Oklahoma: Household Gender Age Birthplace SELF John Seigler M 64y South Carolina WIFE Francis J Seigler F 49y South Carolina SON Morris S Seigler M 13y Oklahoma DAU Dorthy Seigler F 23y South Carolina 1920 census record here: https://familysearch.org/pal:/MM9.1.1/MJ9Z-QPH
[They're also on the 1910 census in Comanche Co, OK ~ jer]
TX Dth Idx thru 1976. Although Pearl died in TX you'll note her residence was in Lawton, Comanche Co, OK. I would look for her obit there, survivors are usually listed and a good way to pick up married names of female members of the family.
Name: Pearl Saxon Death Date: 05 Oct 1947 Death Place: Tremont Clinic, Dallas, Dallas, Texas Gender: Female Race: White Death Age: 52 years 10 months 9 days Estimated Birth Date: Birth Date: 26 Nov 1894 Birthplace: South Caroline Marital Status: Divorced Spouse's Name: Father's Name: John Marshall Seigler Father's Birthplace: South Carolina Mother's Name: Frances Jane Mother's Birthplace: South Carolina Occupation: Housewife Place of Residence: Lawton, Comanche, Okla. Cemetery: Burial Place: Lawton, Okla. Burial Date: 05 Oct 1947 Additional Relatives: Film Number: 2218730 Digital Film Number: 4005472 Image Number: 2479 Reference Number: cn 41388
I'm guessing most of this family lived and died in OK. But did find a "possible" match on the CA Dth Idx:
Seigler, Morris S., b 2/12/1906, OK; d 8/18/1970, Orange Co, CA, age 64 yrs.
Maybe with this info some of the researchers who browse this forum can build on it. Some have access to sources I don't have and they're really good.