Son of Jonathan Beckwith and brother of Penelope.[1]
Jennings's age at death and his age when recommended for an army commission don't quite tally, but they're only a few months out. 1762 is a compromise birthdate. He can't have been much younger if he actually was a Captain in the War.
Married Catherine Miskell, made famous by mistake as "Miss Kill". (There's a rumour that Jennings had an uncle Roger Beckwith who married a Winifred Miskell, probably Catherine's aunt, and probably Winifred Dalton's daughter - if she was, then Jennings's wife was his 2nd cousin, by descent from Mary Newman.)
Described as "Sir" in his obit, though it seems doubtful that he actually took up the title (listed by Burke's etc as long extinct, though perhaps more likely it's only dormant).
There's some confusion over which newspaper the obit appeared in, but it may have been in several. If it was in a paper a long way from where he lived and died, you'd expect it to be in a more local paper as well.
Said to have died at Mount Airy, a very well-known house. Perhaps he died suddenly while visiting the Tayloes. Or perhaps he died at home at Belvoin "near Mount Airy" and the story evolved a bit.
Said by some modern writers to be the father of James Pierson Beckwourth the "African-American mountain man".
Featured German connections: Jennings is 16 degrees from Johann Wolfgang von Goethe, 21 degrees from Dietrich Bonhoeffer, 19 degrees from Lucas Cranach, 20 degrees from Stefanie Graf, 18 degrees from Wilhelm Grimm, 15 degrees from Fanny Hensel, 23 degrees from Theodor Heuss, 15 degrees from Alexander Mack, 30 degrees from Carl Miele, 15 degrees from Nathan Rothschild and 17 degrees from Ferdinand von Zeppelin on our single family tree. Login to see how you relate to 33 million family members.
I also believe that it was *probably* "Sir Jennings" based on R. M. B. Beckwith's probable death in St. Louis en route to see his father out west. As old books of this type go, I've found "Some Prominent Virginia Families" to actually be credible. It gets bonus points with me for spelling "Ranson" right.
However, to add to your points of doubt is Beckwourth's own words -- he was third of thirteen children with two older than himself. That doesn't work with the older children of "Sir Jennings" and record of only two full siblings of Beckwourth's.