Your information states:
Their son Joel Bird Hembree b 26 Nov 1804 in Roane County, Tn d 11 Apr 1860 in Whittenburg, Greene, Mo m Sarah "Sally" Willhite b 20 Mar 1809 in Tn, probably Roane County d aft 1880 in Mo; Father John Willhite/Wilhoit b abt 1783 m Letta "Lettie",an Indian maiden, b abt 1785 in Tennessee. Family records state that she lived in the hills in Roane County, Tn. John and Lettie had several children: Mary "Polly" (wife of) Col Joel Hembree (family records record he was a cousin to Joel Bird), Sarah wife of Joel Bird Hembree.

I wanted to share what I have found in the records of Roane Co, TN.
Sarah Willhite was the sister of mary "Polly "Willhite and daughter of Elijah Wilhite, he was b abt 1778 Washington Co, NC . Have court record that summons them to court to testify in a case for Elijah Wilhite, (their Father) Mary (Polly) did NOT marry Col Joel Hembree. She had 3 children by him out of wedlock and he went to court to legitimize and give them his name. They were Amanda Melvina, Nancy Caroline and Joel Dallas. ( 26 Oct 1847)