I, like you, don't believe the Thomas who married Margery is the son of Erasmus.I do believe that Erasmus' son moved to KY with the Boone, Bryan and other settlers.
The term "brother" 200 years ago did not necessarily mean a sibling, but was used for close relative and could include cousins, as well as closer family.
Some say that Thomas who married Margery is the son of Zachariah Allen whose will is in Orange County, TN.His will does not mention a Thomas, but does mention a Zachariah (Jr).I believe that Zachariah (Jr.) has been proven to be the Zachariah in early IL.
Some say that Zachariah of Orange County was born in 1735 in Baltimore, MD.I've found no evidence of that, but have determined there are Zachariah Allens in Baltimore in 1790 who might be the one born in 1735.
Thus, we're left hanging with this question:Who is this Thomas Allen who married Margery?Is he related (nephew, cousin, etc.) to Erasmus Withers Allen who lived near the Bryans?If not, how did he meet her?
Back when I placed the original post, I was trying to determine relationships between Zachariah Allens in order to find siblings for Erasmus Withers Allen's grandfather, John Allen, b. bef. 1650.I had no idea that all the Z's in the 1700's had been commingled.I've now identified EIGHT Z's between 1700 and 1800 and at least one in the 17th Century.
E-mail me if you'd like to join a bunch of us trying to sort Allens.