Linda, Have you discovered the parents of Nathan Allen who married Aletha Doyle and settled finally in Greene County, Illinois.
I believe that Thomas Allen m. Margery Bryan 1789, Rowan Co., NC were not the parents of Nathan.I have copies of the final settlement papers for Thomas Allen b. 1766.The children all signed and Nathan Allen was not one of the signatures.Also, the location of Patterson is pretty far removed from the locations of Thomas and Margery's children's land entry records.
I would be very much interested in information you have on Nathan Allen, since it might help establish the parents of Thomas Allen who married Margery Bryan.
There seems to be a connection between Daniel Allen Who married Althea Hale in Tennessee in 1788 and the move of his daughter Sarah Jane Allen m. John Davidson to Lawrence Co., Missouri.Around 1850, three sons of Thomas and Margery's moved to Lawrence County, Mo.I don't know how common the name ALTHEA was. It might be a clue. Jane Vandersand