Your research is right. Ann did have a brother who was Edward from Orcheston St George. But if there is no dna match between you and me (or at least our fathers) that must mean then that the Edward Mortimer of Orcheston St George is not my Edward. Which means I have eliminated him from my enquiries which is good (and bad as it means returning to the drawing board).
So, my Edward isn't the one baptised in Trowbridge, Ogbourne St George or Orcheston St George. Can anyone suggest any other avenues? Could he be from the Avebury Mortimers but not baptised? Is he from outside of Wiltshire? Hmm.