Many websites assume that John S. Pemberton is the nephew of John C. Pemberton, but I cannot find any sources for this. John S's father was James C. Pemberton, born in North Carolina sometime around 1803. Most sources assume that the C stands for Clifford and is thus the brother of John Clifford Pemberton, but John C's parents were not married until 1812, they never went to North Carolina, and no family histories mention James. A more likely ancestor would be Richard Pemberton and Amy Stith, explaining John S's middle name.