My sincere apologies for the delay in responding to your message. I don't check this forum nearly as often as I do the Abernathy one.
I know little to nothing about the ancestors of Elizabeth Brouse. What I do have about the ancestors of John Abernathy b. 1772 is that he was clearly NOT of the lineage that leads back to the 1st Robert Abernathy of Charles City County, no matter how many online trees to that effect one finds. This is because the Y-DNA of a direct line (male only) living descendant of John does NOT match the many direct line (male only) living descendants of that first Robert. Instead, John Abernathy, b. 25 Sep 1772 in Bath (Berkley Springs), Morgan Co, (now) WV, d. 5 Oct 1855 Darlington, Montgomery Co, IN was of a lineage that descends from William Abernathy, formerly, we believe, of Northern Ireland and wf Sarah Samuels of County Antrim, Northern Ireland, making John's ethnic background a Scots-Irish one rather than a mainland Scotland one. You see, at the time that John was born in Bath west of the Shenandoah Valley to the alleged parents found on many online trees that led back to the 1st Robert, those supposed parents were living in lowland counties along the border between Virginia and North Carolina, and miles away from that portion of the Shenandoah Valley of Virginia that now contains the town of Bath.
We now are reasonably sure that John Abernathy (1772-1855) was the eldest son of James Abernathy (d. 24 Nov 1824 Morgan Co, now in West Virginia) & Anne Clarke and therefore grandson of William Abernathy (d. in the fall of 1780 in Winchester, Fredrick Co, VA) and Sarah Samuels of County Antrim, N. Ireland.
I hope this is of some help to you. Bottom line: scientific evidence forbids that particular John Abernathy from being part of the family descended from Robert Abernathy of Charles City County VA.