I've got very little information on the Sweatts, but it may be a bit helpful to you. I'm from part of the Barber line of Melungeons (google this if you're unfamiliar) also from SC, GA, AL, and TX. The Sweatts seem to be a very distantly related family that married twice into the Barber family (not like inbreeding or anything--more like one of those cases where two sisters married two brothers, if that makes any sense. Not all that uncommon in the rural southeast.)
The only name I have definitively verified, is Luther Sweatt, who, some time in the very early 1900s, married a Barber woman (first name unknown), who was one of the children of John Wesley Barber (1880-1958) and Lucy Campbell (1883-1962) of St Clair County, Alabama. Luther identified himself as Portuguese or "Portyghee"--something that you might be interested to hear if you're interested in Melungeon history.