Some support for your post on William and Phebe Plumly (Plumlee).
William and Phebe's family broke up into three parts. Although this is not 100% true, we find that the group that went to SC and GA used the PlumBlee spelling, The group in NC retained the Plumley spelling, and the group that went to TN, IL, AR etc used the Plumlee spelling.
However today you will find all three spellings spread across the US. Have found no evidence of "three brothers." I have heard claims of "four brothers from England also." One candidate for William's father is Matthew Plumley who was sentenced in Feb 1727 and was imprisoned in Newgate Prison in London and Transported on the ship Rappahamock to MD in 1727. He was imprisoned for fighting against King James in the Monmouth War in Somerset England. It has not been proved that Matthew is the father of William, just a lot of circumstantial evidence. Matthew's wife was probably Abagail (no surname.)
Perhaps this will give you some area's for further research.Due to age and health I have about given up on any research.