The only documentation I have is from "THE McGAVOCK FAMILY. A Genealogical History of James McGavock and his Descendants from 1760 to 1903", by
Rev. Robert Gray, page 79 (published 1903):
"Cynthia KENT, 255, daughter of James R., born in Montgomery county, Va., 16 July 1820, married Dr. Henry Moss BENTLEY, 14 March 1837. He, son of William Weldon BENTLEY and his wife Lucy Gaines TURPIN, was born in Powhatan county, Va., 25 April, 1807, and died 19 December, 1846. he was an eminent physician, a polished gentleman, and as such highly esteemed. She died 7 December, 1883."