Not really connected, but just in case it helps:
Mary Waller Johnston (born 1759 Spots. VA - died 1788 SC) married a Cason (no first name known). Mary's parents were Henry Goodloe Johnston (1727-1802) and Mary Waller Johnston (1759-1788). Henry Johnson (the "t" is omitted in many records) witnessed the deed of land by Edward Cason to his daughter in law, Susannah in May 1766 in Spotsyvania Co., VA.

Not sure if Mary Johnston's husband was son of Edward, but seems likely.