There is a marriage record in Surry Co. NC for a Joseph Coker and Mary Brown in April of 1800. I know it's a stretch, but is still possible, esp. if she was his 2nd wife and much younger. The 1830 fed. census for Franklin Co. TN has 2 Joseph Cokers, both with at least one female under 5 years old. However, reported males wouldn't be old enough to have been married in 1800...still, interesting.

My Cokers in TN were in Monroe/McMinn and Polk Counties, but most moved to Hamilton Co, IL between 1830 - 1850. I have a Joseph, but he is born 1819 and is son of William Coker and Catherine Huffman. Good luck on your search!
Mary