Synchronistically, I was just in my car running an errand and listening to a BBC Radio program about a huge gathering of people named Jones in Wales trying to break a Guinness record. There was a geneticist on explaining how these Joneses were all descended from men whose first name was John when the English forced the Welsh to take "regular" last names. He said they were no more likely to be related than the average degree of relatedness for Britain which is 6th cousins.