The 8% Error?

[skauwt]

deleted

[O'Callaghan]

If you get back as far as when people actually lived as a clan, on common land, many were not blood related, but merely joined the clan. In Scottish clans they may have been defined as a sept (same clan, different surname in that context), but in Irish clans (called septs by some, to confuse us) I'm told they often took the surname of the clan. However, over time, they would most likely have intermarried with other clan members, and wound up related by blood after all. And those 8% may have had the 'wrong' father, but that might not have affected whether they were related by blood to the clan.

Of course, in more modern times, it's all different.