He may be connected to the York SC Grahams. I have a Robert and James Graham disappearing from there after 1830. The only other Robert Graham in the 1830 SC census stayed put in 1840 census. Robert of Lafayette MS named his apparent first son the somewhat infrequently usedArchibald and James named his Matthew. These were the names of the (other) brothers of James of York SC.
Robert appears to be their brother, although not explicitly mentioned in the estate papers. He was a big buyer at the estate sale, but he did not sign a receipt, presumably because his part was deducted from what he owed. Five heirs were mentioned, but the estate (less the widow's 1/3) was divided among 6 people.