See https://www.indianreservations.net/2016/12/jacob-castle-and-sowega-...
conclusions
1. From an historical standpoint there is quite a bit of information on Jacob Castle. He lived a tough frontier life at the edge of the 'white world.' There is no doubt that he would have encountered Native Americans during his hunting trips. But, there is no proof that he married an Indian woman. Some DNA results from possible descendants show no NA DNA. While this does not rule out native ancestry, it doesn't help either.
One big problem with the historical record is that it is unclear if the information after 1764 belongs to Jacob Castle or a son Jacob (Jr). For instance, who was it that fought at the Battle of King's Mountain, Jacob or a son. Jacob would have been almost 65 years old at the time, a bit long in the tooth for a forced march through the mountains. Who was the Jacob who bought land from John Donoho and his land warrant in 1782? This is most likely the man who is enumerated in the census' of 1830 and 1840 and not the elder Jacob.
A Jacob Castle was recorded as paying taxes in Rowan County, North Carolina in 1768. Was this our Jacob Castle? Whoever he was he had established a homestead there. The name Jacob Castle was not rare, searching ancestry show quite a few men of that name.
In 1779 a Jacob Cassell paid £240 for 600 acres of land, Treasury Warrant 945, on Pottinger Creek in what is now Nelson County, Kentucky. A year later he turned it over to his son Henry. Henry Cassell is found in subsequent census' in Kentucky. There was also a Henry Castle in West Virginia. There is nothing that ties these men together.
2. From a genealogical standpoint we know very little about Jacob Castle. There is no source for parents, wife or children. Maybe somewhere in some yet to be digitized archive there will be some document which will reveal some information that can help us identify his family.
3. DNA can help unravel the claims of descent from Jacob Castle. Familytree DNA has a Castle project. Two kits claim Yelles Cassell, grandfather of Peter Cassell, as their ancestor but these kits do not match. Nor do these match the kit who claims descent from Jacob Castle 1749-1849 who I believe is the man claimed to be the son of Jacob Castle. None of the DNA results match the kit which claims Elijah Castle of Russell County either. More men need to take the yDNA test to sort out potential relationships.
4. The Shawnee Heritage Books should be viewed as fiction. Chief Ben Barnes, to put it mildly, has a very low opinion of these books. If you believe that you have a Shawnee ancestor call the tribe headquarters in Miami, OK and they will help you if they can with your research.
5. Sowega "Gliding Swan" is an internet/Don Greene myth. If you are committed to a proven, well documented, well sourced genealogy, then she has no place in your tree.
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If anyone knows differently, please post.