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Basic cousinship.

01/24/2009

Cousinship between pesons is determined by their common ancestor (the person from whom both are directly descended).

There are more complicated cousin relationships that I make no claims of understanding, but I have figured out the basic pattern for determining one’s cousinship.

A shared grandparent makes two persons first cousins.

A shared great-grandparent makes them second cousins.

A shared great-great grandparent makes them third cousins.

As long as both persons are descended in the same way, the pattern holds.

In the case of one person being fewer or more generations separated from the common ancestor, the cousin relation that would exist if both persons were related as the person with fewer generations separating him from the common ancestor, is used. To be removed means there is a generational difference. In other words, a grandchild and a great- grandchild of the same person, are related as first cousins, once removed, not second cousins, twice removed. Likewise, a person’s great-great-grandchild and great-great-great-great-grandchild are related as third cousins, twice removed.

When one person is a son to the common ancestor, the other person is always his nephew/niece, then grand nephew/niece, then great-grand nephew/niece, and son on.

Hopefully, if I was clear and concise enough, the pattern can be recognized, and fewer people will need to refer to cousin charts to understand how they are related if they only know who their common ancestor is.

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