Post by wjhonsonI cite the Vis Essex, and *fix* their descent by moving her up one generation, so she is not the daughter of, but the sister of. Seems a more likely mistake than that her grandchildren didn't know who their grandmother was.
So...you've made a guess, in order to "fix" the Visitation of Essex. Aside from the visitation pedigree, do you have any evidence that Joan is even a Percy? I'm not aware of ANY Percy pedigree that shows a Joan that could be this person.
Two comments from Brad Verity in the discussion of March 2013 that you initiated in this matter (in relation to the royal descent of Graham Greene) seem appropriate to bear repeating:
"If the only evidence that Arthur Harris's wife Joan was even a Percy
in the first place, is the Harris pedigree from the Visitation of
Essex, I wouldn't put too much weight on it. That particular Harleian
Society volume is full of errors within the pedigrees, which are
hodgepodged together by the editor and not necessarily the official
versions from the College of Arms."
and:
"So the parentage of Joan, wife of Arthur Harris, remains uncertain.
If she was a Percy, it's not clear where she fits into the family,
though, due to chronology and other evidence, she could not have been
the daughter of the 5th Earl of Northumberland & Katherine Spencer,
nor of their son Sir Thomas Percy & Eleanor Harbottle."
I think you should give up on this particular Edward III descent.