I've been working on a new Tankersley genealogy for the past ten years and have amassed a huge volume of data, a lot of it from other people's records, which means I can't personally document it. I checked my manuscript, which is still far from complete, and here's what I found on your family. As I said, I can't document this beyond giving you the name of the original source, but I hope it helps.
(LINE R.)GREEN B. TANKERSLEY. According to the records of his descendant, Letha M. Williams of Big Spring, Texas, he was born in North Carolina c.1795. His first wife was Emily, last name unknown. His second wife was Sarah Haynes/Cole, nee Harbour. He, his wife Emily (born in Tennessee c.1805) and their children were enumerated in the census of Lavaca County, Texas in 1850. This census gives his birthplace as Tennessee. He died in Lavaca County in 1869. He is probably the Greenberry Tankersley enumerated in the 1830 census of Shelby County, Alabama.
If he was actually born in North Carolina, but perhaps grew up in Tennessee, the most likely possibility is that Green B. Tankersley was a descendant of William Tankersley (Line J). In 1820, a William Tankersley, born before 1775, was enumerated in the census of White County, Tennessee. There are some indications that this William Tankersley may have been a son of William (J). Two of his sons in this cen