I have a document showing a Graves Kimbrough as the 5th son of Thomas Kimbrough and Eleanor Graves (Caswell County). Thomas was born ca 1690 and died in 1777. Their son Thomas Jr. was born around 1742 and married Elizabeth Graves in 1792. From the birthdate, your Rufus Graves Kimbrough looks like he would be a grandson of Thomas Jr. Details are sketchy on Thomas' line. Hope this is helpful. I got an inquiry from Scott Stodola on this board, who appears to be researching the same line as you.