Hello Peter: email me at firstname.lastname@example.org so we can compare data since as you noted you fall into the little group that the MacFarlane DNA Project indicates as MacGregor.
As far as I can tell every one of the men in that group relate to the same branch line off the MacGregor stem... does this mean that we have a common ances. ie, the one who decided to swap MacGregor for MacFarlane/McFarland, maybe...not so sure...as the ances of one of the men does not have seem to have split for Ireland but stayed on in Scotland (but I guess that the common male could have run off to Ireland then went back to Scotland and left a child there then ran back to Ireland; maybe he had a son who left Ireland and went to Scotland, and with the McFarland name avoided the English). BTW the Ulster Irish origin for this group is pretty common.
I should like to know more about this McFarland Family that claims that a Walter McFarland was the brother of the mother of Rob Roy...since the mother of Rob Roy was a Margaret Campbell...also can you add a little more to this "Tabby McFarland" daug of a "Duncan McFarland" from Tenn?
Since the DYS markers are so similar I would guess that you are off the Duncan McFarland and Ann (or Elizabeth) Porter line here in Virginia.
If you establish that you are not related to the Duncan mcFarland line of VA and can establish a "new" McFarland/MacGregor line in NC... you note one of 4 brothers... this would be very interesting.
Can you give me a little more ion these 4 brothers?