When's the cut off point? 100 years? 1000 years? Could go back far enough, probably find my ancestors on the British side came from what is now Germany, being that those that populate Britain tend to descend from Saxons or Scandinavians, so as they were not from Britannia, am I German, or Swedish? Personally I think as far back as you need to go is grandparents as far as nationality is concerned. If your grandparents were all born in America/Australia, then you are very much American/Australian. You can talk about DNA and then we all get parcelled into European/Asian/African, but what's the use of that?