Hi KH,
In addition to this possibility that Mary may in fact be the daughter of my Robert Knox -- and that the registrar got the names mixed up when recording (George Haldane's father was deceased at the time George & Mary married) -- I'm also investigating some theories about the antecedants of Robert Knox's father, John Knox. Have decided to splurge and hire a professional genealogist to see if I'm on the right track. Will let you know if anything interesting comes up.