Robert A. Moody may well have been a brother of Thomas F.; however, Robert reported himself on censuses as born around 1820. No Moody from the Guilford County group appears of the right age to be parents to both Thomas F. and Robert A., and only an older Thomas F. seems logical as Robert's parent. They belonged to the Moody-McCuiston clan as shown by Isabella McCuiston's will and by Robert F. McCuiston's being Robert's bondsman for his December 1844 marriage to Abigail Rayl in Guilford County.
Thomas F. Moody witnessed the will of Isabella McCuiston in Guilford County 8 September 1841. Thomas was deceased by May 1844 when the will was recorded in court after Isabella McCuiston's death. Robert A. Moody testifies then to Thomas's death that the signature on the will was that of Thomas. (next image after image of will)
Link to copy of will and court acceptance courtesty of Fredric "Rick" Saunders
Source: Wills and estate papers (Guilford County), 1663-1978, North Carolina. Division of Archives and History