Marshall....I do not know for certain just who that John Brown and Thomas Brown were.If they were also members of DNA "Group 33," then they certainly could have been descendants of that George Brown/Miss Rowland family that I SUSPECT was perhaps one of the earliest people in "Group 33" in VA.That George Brown (born in the 1600s) fathereda son who was named Thomas Brown, Senior (who married a Miss Thornton who was a daughter of a Luke Thornton), and Thomas "Senior" fathered a son who was named Thomas Brown, Junior....and Thomas "Junior" married a Miss Read/Reed/Reid who was a Coleman descendant.That is why one of the sons of Thomas Brown, Junior was named Coleman Brown, and that may be why some people have confused "Group 33" with "Group 10" (since both unrleated families had men in them who were named Coleman Brown).
Note: Per my research, the above Miss Reed did not "trace back" to Robert Coleman, Senior and Elizabeth Grizzell, nor back to Robert Coleman, Junior and Ann Spilsby.I would not be too surprised, however, if her Coleman ancestor was a brother or other close relative of the Robert Coleman, Senior who married Elizabeth Grizzell (but no proof).
There was also a John Brown who married a Mary Oxford, and they came into Culpeper Co., VA from King William (or Prince William?) Co., VA, as I recall.I have reasons tobelieve that this John Brown was also a member of DNA "Group 33."As I recall, that John Brown and Mary Oxford also had a son who was named Thomas Brown....so maybe they were the ones involved with the 1780 Will of Mr. Zimmerman in Culpeper Co., VA that you mentioned.The above is about all that I know at this point.
Oh, by the way, Gary Brown in "Group 33" found a living male Brown descendant of the above Thomas Brown/Miss Reed family, and he was trying to get that Mr. Brown to take the DNA test.I guess we'll see if that comes to fruition.As I recall, the James Brown who died in Culpeper Co., VA around 1823 named a son George Coleman Brown, and a descendant of that James Brown is also in DNA "Group 33."