You could try to go to familysearch.org and locate this census data. It has the birth month/year/location for Josephine and John. Also the birth location of their parents.
It also lists 5 of their 12 children. Maybe from that starting point you can find out more details. Myrtle and George Wren are on the second reference.
United States Census, 1900 Mississippi Prentiss 0098 Beat 3 (excl. Baldwyn town)
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Name: Josephine Whitlock
Residence: 0098 Beat 3 (excl. Baldwyn town), Prentiss, Mississippi
Birth Date: Sep 1852
Birthplace: Alabama
Father's Birthplace: Tennessee
Mother's Birthplace: Alabama
Relationship to Head of Household: Wife
Spouse: John G Whitlock
Birth Date: Sep 1848
Birthplace: Alabama
Father's Birthplace: Ireland
Mother's Birthplace: Alabama
Marital Status: Married
Years Married: 30
Estimated Marriage Year: 1870
Mother How Many Children: 12
Number Living Children: 12
United States Census, 1900 Mississippi Prentiss 0099 Beat 4 Marietta Precinct
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