Without clear and undisputed documentation there is always confusion concerning people of the same name who lived at the same time!
Gabriel Alexander in Augusta County, Virginia was somewhat older than Gabriel Alexander in Iredell County, North Carolina. And although Gabriel in Augusta had a son named Gabriel, the latter one is apparently accounted for and never lived in North Carolina. Gabriel senior in Augusta did not have a son named Josiah. So we rule them out as the recipients of Rebecca (Alexander) Emmitt’s largesse.
Rebecca (Alexander) Emmit or Emmitt wrote her will in Chester County, Pennsylvania in 1785 and it was proved in 1792 without a codicil. One would expect to find Josiah Alexander, son of her brother Gabriel, in the 1790 census in Pennsylvania if he was living there as you said. I find no such person.
I do not mean to say that Rebecca Emmitt’s brother WAS for sure Gabriel of North Carolina – just investigating whether or not that is even a feasible possibility.
There is no way of knowing whether or not Rebecca Emmit would have left a bequest to a nephew she had never met. We don’t even know if she ever did meet with any of her siblings or nieces and nephews who settled far from Chester County. People traveled long distances for prolonged visits. She would have made her choices for purely personal reasons that we will never have any knowledge of. So to say that she would not have left a bequest to Josiah Alexander, son of Gabriel, in North Carolina just because she had never met him is not a valid argument.
At no time in her will did she mention WHERE any of her heirs lived. So to say that IF she meant Josiah Alexander of North Carolina she would have said so is also not a valid argument.
You may be completely right – that your Alexander family in the region of Iredell/Burke counties in North Carolina were not the siblings and nephews mentioned by Rebecca Emmitt in her will. But your arguments of why not just don’t hold up to scrutiny.
Gabriel Alexander first appeared in New Garden, Chester County, Pennsylvania tax lists in 1721. The Emmitts were already there by 1719. Along with Gabriel was John Alexander and because the latter’s given name is so common we cannot be positive that this is the same John married to Susanna who had known daughter Rebecca Emmitt – but the circumstantial evidence would seem to point to that probability.
Meanwhile John Alexander was taxed in London Britain beginning 1725 where he lived until his death at which time Susannah Alexander was on the tax lists until her death. New Garden Township (where both Gabriel and John lived until 1725) was divided into New London and London Britain in or about 1725. I suspect that these families did not actually move but rather that the township name changed around them.
In 1725 Gabriel Alexander was taxed in New London Township, Chester County and remained there through 1730; in 1732 ‘widow’ Alexander and later Mary Alexander was taxed in his stead. There were no other Alexander families living in New London at this time – so, again, circumstantial evidence would seem to point to widow Mary Alexander being the widow of Gabriel.
It would be very nice (even essential) to have yDNA information on these Alexander families to see (1) if they were related to the other Alexanders in Cecil County, Maryland and (2) if they were related to each other. Because the paper trail / documentation for these families is so poor and because I don’t trust the suppositions and hearsay posted online for these families, I believe we can’t come to any conclusions with great assurance.