Edwin, Just a thought. I show Birth dates of James, Joseph, Martha the same as you do, however, I show Hugh was born ca 1741 and married Elizabeth Smith in 1774. Jane was born ca 1762 and married in 1769 and George born ca 1744. This makes a little more since. Hugh married Mary Kent 10 April 1780. He died between 4 Sept 1817 and Nov 1817.
Your Nancy was sister to my Elizabeth Cunningham. Elizabeth married John Trentham in 1819. By the way, I do show Nancy married William Cunningham on 25 Dec 1816. He was born in 1801 in NC. They had no children that I know of. Then married Levi in 1825 You probably know all this. I was also told Joseph Cunningham born ca 1710 may have been married to an Unknown Dupree born abt 1712. No proof that I have. Joseph's will was dated 6 Mar 1769 and probated 8 Mar 1769 so must have died before Mar 1769. Also was told that Joseph's father could be a James Cunningham born abt 1693 and died 1743. Mother could be Sara Belle born 1695 died 1711. Just another part of the puzzle.
Please keep me in mind if you find out anything else. Thanks, Sandi firstname.lastname@example.org