My Sweatt York/Lancaster County line is from William Lane Sweatt born about 1791. Two of his children were Margaret M. Sweatt b.1847 and William A. Sweatt b. 1859. Your William Lowery Sweatt of York County is probably related. There were several Sweatt families in this area of South Carolina and William seems to be a family name. I have not done much work on the Sweatt line to date.