I have been working the Andrew Forgey parent problem from several angles. Collecting as much as I can from records generated in his lifetime is one strategy. The only thing I have gleaned from this is the fact that he was born in Tennessee, he consistently stated this in every census. I have located his obituary in the Davenport Iowa Democrat which states he was born in Knox County, Tennessee.
Another strategy has been to trace all 15 of his children in hopes that they may have mentioned the names of Andrew's parents. I have located some county history bios and obits. Only Elias mentions his father's origins:
I've also worked the problem by searching his stated Tennessee birthplace records. By process of elimination I came up with Hugh Forgey and Catherine Fisher as probable parents. I have not found Catherine Fisher in any records generated during her lifetime. I have only found her mentioned in Donald Whyte's A Dictionary of Scottish Emigrants to the USA and Palma Carmen Scheumack's Reynolds family letters with the journal of Robert Bannon Reynolds.
I have been able to find Hugh Forgey's probable father in records generated during his lifetime here is a timeline based on those records: http://sites.google.com/site/theforgeys/hugh-forgey-timeline-begins-1786-ends-1809 There are no censuses for eastern Tennessee before 1830.