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This will probably only confuse the matter. I don't have "Royston," but I do have "Rayston," and a Robert Rayston Marable at that. The dates are wrong (this R.R.M. would not have been born before about 1825, so yours would have been a cousin of his father, Edward).
Edward Marable (b. 1805, Norfolk, VA) had a wife Lucy (surname unknown) and children Thornton S., Robert Rayston, Thomas Edward, and Ann Elizabeth.
In this Marable family, there is a close association with the Pennington family of Sussex Co., VA.