Joseph G. Grisham from Pittsylvania Co.,VA

I am looking for any information on Joseph G. Grisham. He was born on 18 Nov 1795 in Pittsylvania Co.,  VA, married in 1820 to Nancy White (Overton) who was born 1797 NC, moved to Smith Co.,TN in 1826, & died on 1 Sep 1875. Their children were: William Pryor, Martha Patsy, Nancy B., James Watson, Celia, Timothy Nelson, & Joseph C.  I have a copy of a family tree that was given to my father & his siblings that said "Some ancestors say Joseph or parents came from Ireland thru Overton Co. to Smith Co.,TN". It listed a Sarah (King) that was a sister-in-law of Joseph, but did not give his brother's name or their parents' names. How do I find out if they came to TN by themselves or if any relatives went with them?