Have you taken the YDNA test? If not consider doing so. Many people claim that Ebenezer R. Alexander from Logan County, KY, was a sibling of Matthew and William and a son of James of Spartanburg; however, there is nothing so far to support that except for his having been in Logan County at the same time as they were. If you are willing to take the DNA test at the 37-marker level or higher, the results would almost certainly tell the tale since we have results for about a dozen of the descendants of James of Spartanburg from at least three sons plus results from a few who may descend from James or from a brother or cousin of James.
Roger, who will likely provide an answer here, is the coordinator of the DNA project.