Hi Callibaba,
I don’t have Agnes Thoburn’s father Joseph attached anywhere to the wider Thoburn tree. There are several Joseph Thoburns listed by William Fee McKinney [WFM] and in the Irish American Thoburn [IAT] book:
1. Joseph Thoburn (c1690-1758) m. Agnes Russell. [WFM/IAT]
2. Joseph Thoburn (b. 1719) m. Eleanor Barron. [IAT] Nephew of #1?
3. Joseph Thoburn (b. 1750) m. _____ _____ [IAT/WFM] GS of #1.
4. Joseph Thoburn (b. 1759) m. Janet Bigger. [IAT] Son of #2.
5. Joseph Thoburn (b. 1771) m. Nancy Coey/Coley [IAT/WFM] Son of #3
6. Joseph Thoburn (b. 1788) [IAT] Son of #4
Josephs #1-4 are probably too early. Joseph #5 died in 1853 according to IAT, but I’ve not found any record of that. Joseph #6 is a possibility – I have no record of whether he married or when he died. Ah, you’ve got him in Scotland so that rules him out too.
He could be a Joseph Thoburn not listed by either WFM or IAT, in which case the most likely place to put him would be a son of David Thoburn (c1757-1802) as suggested by Linda. This David was son of #2 and brother of #4. He lived at Roughfort which fits.
David Thoburn married Janet Barron in August 1783 according to IAT, so there is plenty of room for him to have a son Joseph born c1790 who could have been father of Agnes Thoburn who married John Adams.
With David’s wife and mother both being Barrons, it is quite likely he inherited land from that family in Roughfort.
Gilby
p.s. I’m also a match to the same Maybin/Adams/Thoburn person on FTDNA. I emailed them in 2017 and 2019. No response