Judy, I have no difinitive proof whatever to support a theory that might clarify this, but will offer it for anyone to prove or disprove.
Among my notes for the David who married Martha Ann Turner, I find the comment that Judge McCorkle adds a daughter Martha who married a Robert Abernathy. I also find on my notes for daughter Martha "Patty" the following:
md. (as a widow) 3rd cousin David Abernathy, son of James.
I find it highly suspect that this couple would have two daughters both named Martha, both of whom survived to adulthood. The only explination that I can conjecture (and it is JUST a guess) is that there was only one Martha and she first married a Robert Abernathy and then when he died she married David. This does not offer any clue as to who the Robert she might have married was, however.
And since it's only a theory, I can advance no proof.