Excerpt from a letter I recently sent my parents:
"Dear Mum & Dad
I have discovered that you both have a common ancestor in John de Braose (1198-1232), Lord of Bramber (in Sussex) and Gower (in Wales). Attached is a printout of how you both trace back to him, as well as a short bio of his life. His wife Margaret was a daughter of Llywelyn, Prince of Wales, whose wife Joane was an illegitimate daughter of King John. So now you both have lines of royal descent. Look in the library for the historical novel
Here Be Dragons by Sharon Penman, it is based on the life of these people and is a very good read.
This therefore makes you in geneological terms 23rd cousins, once removed. The attached Table of Consanguinity
http://www.heirsearch.com/table.htm may help explain how cousin terminology works, if you didn’t already understand it. It also shows the degrees of relationship. Most cultures regard anyone within 7 degrees of relationship to be family, and intermarrige with relatives of 4 degrees or less, or sharing the same surname, is strictly taboo. Remote communities with a population less than 1500 struggle to find suitable partners, so have developed intricate rules of marriage to prevent inbreeding. This is evident in some Aboriginal language groups, as well many small island societies around the world, such as Easter Island. "
Cheers
Nudge