I'm not related/acquainted. Initial research found John Isom Jackson wed Virginia Brown 1 May 1863 in Hopkins, TX then P. R. (Polly Rebecca aka Mary Rebecka) Jackson 5 Dec 1879 in Jack, TX. A family tree, viewable https://familysearch.org/
, indicates Virginia's parents were George Alton Brown and Mary Polly McClinton. At any point in time there might be several people with the same/similar names and/or similar vitals? You need to share more detailed info to facilitate research. Start with names/births of your grgrmother and the family that raised her?