There was a James Duncan, married to a Margaret McQuillin, who was living in Lawrence Co., IN in 1838. He apparently sold his interest in a lot in Lexington that was his (or his wife's) share of the estate of an unnamed Mcquillan to one John M. McQuillen of Fayette County, KY. The deed was witnessed by my 3rd great-grandfather, Enoch Hampton, husband of Lucretia Duncan.
Could Margaret McQuillin and John M. McQuillen be siblings of your Thomas?
My real interest in this is discovering the relationship between James Duncan and Lucretia Duncan, and in discovering the parents of both Lucretia Duncan and Enoch Hampton, who married in Clark Co., KY in 1831. A James Duncan was surety on the marriage bond. Whether or not he was the same James Duncan who married Margaret McQuillin on 15 Jun 1837 in Fayette Co., I don't know.
Any information on these Duncans would be much appreciated!