GENEALOGICAL RELATIONSHIP RULES
* 1st cousins always share a common grandparent
* 2nd cousins always share a common great-grandparent
* 3rd cousins always share a common 2nd great-grandparent
* 4th cousins always share a common 3rd great-grandparent.
(The “great” always being one less than the cousin relationship.)
* 1st, 2nd, 3rd, etc. Cousins are always of the same generation.
* Cousins NOT of the same generation are cousins “removed”. The number of times
a cousin is “removed” depends on the number of generations “away” they are.
“1st cousin once removed” being the child of your 1st cousin.
“1st cousin twice removed” being the grandchild of your 1st cousin.
* This is true of PRECEDING generations of cousins as well. (Though not with 1st cousins since their parents and grandparents would be your aunt/uncles and grandparents).
While the child of your “2nd Cousin” is your “2nd Cousin once removed” (being one generation “removed” from yours), the parent of your “2nd cousin” is also your “2nd cousin once removed” because they are one generation “removed” from your generation as well.
Someone who is a 1st cousin to any of your direct lineage family members (persons you directly descend from or who directly descend from you: your parents, your grandparents, your great-grandparents, your child, your grandchildren, etc.) is a 1st cousin to you, but are “removed”, of course.
The “1st cousin” of your great-grandparent is:
“1st cousin once removed” to your grandparent
“1st cousin twice removed” to your parent
“1st cousin thrice removed” to you
“1st cousin 4 times removed” to your child and so on.
A nice looking PDF document can be viewed or downloaded here that shows these rules very nicely. Click to View This was found on Dick Eastman’s site and created by Betty Eichhorn.
* Mother ~ Father, with their siblings being your Aunt/Uncle.
* Grandmother ~ Grandfather, with their siblings being your Grandaunt/Granduncle.
(Also commonly, though incorrectly, referred to as Great Aunt/Great Uncle)
* Great-Grandmother ~ Great-Grandfather, with their siblings being your Great-Grandaunt/Great-Granduncle, and so forth.
Note: For legal and genealogical purposes the term GREAT does not stand alone for any relative, it is only correct in conjunction with GRAND, as in Great-Grandfather.
GRAND, however, can stand alone as for grandparent and grandaunt/granduncle.
A generation is defined as the average time between a mother’s first offspring and her daughter’s first offspring. The generation length is 25.2 years in the United States as of 2007 and 27.4 years in the United Kingdom as of 2004.
“Imagine a dinner table set for a thousand guests, in which each man is sitting between his own father and his own son. At one end of the table might be a French Nobel laureate in a white tie and tails, and with the Legion of Honor on his breast, and at the other end a Cro-Magnon man dressed in animal skins and with a necklace of cave-bear teeth. Yet each one would be able to converse with his neighbors on his left and right, who would either be his father or his son. So the distance from then to now is not really great.” (From Bjorn Kurten, Singletusk: A Story of the Ice Age, 1986)