Ascertaining Generational Relationships

Kinship Terminology

Cousins

A first cousin is the child of your aunt and uncle (your aunt or uncle is a sibling to one of your parents). If your cousin has a child, that child is a first cousin once removed to you, i.e. one generation removed from being a first cousin. If you have a child, your child is a second cousin to your first cousin's child. If your first cousin has a grandchild, that grandchild is a first cousin twice removed to you, and a third cousin to your grandchild.

PARENT
Child Sibling Child
Grandchild Cousin Grandchild
Great-grandchild Second cousin Great-grandchild
Second great-grandchild Third cousin Second great-grandchild
Third great-grandchild Fourth cousin Third great-grandchild
Fourth great-grandchild Fifth cousin Fourth great-grandchild
Fifth great-grandchild Sixth cousin Fifth great-grandchild

The great-grandchild on the left (above) is a second cousin twice removed to the third great-grandchild on the right (above). Please note that the third great-grandchild on the right is not a fourth cousin twice removed to the great-grandchild on the left; the relationship is still second cousin twice removed.

Accordingly:

  1. first cousins always share a grandparent
  2. second cousins always share a great-grandparent
  3. third cousins always share a second great-grandparent
  4. fourth cousins always share a third great-grandparent
  5. fifth cousins always share a fourth great-grandparent

So the Cousin rule-of-thumb is that the greats are always one less than the cousin relationship.

The above method of determining relationship is:

An alternative method refers to a first cousin once removed as a second cousin; a first cousin twice removed as a third cousin; a first cousin three times removed as a fourth cousin, and so on. This is likely why there is so much confusion on the issue of cousins and removed.

Half-Cousins

The word half means only one of two parents is the blood parent, so where two siblings share only one parent, they are half-siblings. The children of these two half-siblings would be half-cousins, because they share only one of the grandparents.

So, half-cousins are called that, because they share only one of the two grandparents commonly. As far as half-cousin and removed is concerned, the same rules apply as to full cousins.

Double-Cousins

Double cousins are the result of marriages between two brothers and two sisters (of another family). The children of each married pair are cousins to each other, not only by way of their father's family, but by way of their mother's family as well. Otherwise, the same rules apply as to full cousins; so one (whose grandparents were brothers who married sisters) could have a second double cousin once removed.

A Chart for Determining Relationships
  0 1 2 3 4 5 6 7 8
0 CA C GC GGC 2GGC 3GGC 4GGC 5GGC 6GGC
1 C S N GN GGN 2GGN 3GGN 4GGN 5GGN
2 GC N 1C 1C1R 1C2R 1C3R 1C4R 1C5R 1C6R
3 GGC GN 1C1R 2C 2C1R 2C2R 2C3R 2C4R 2C5R
4 2GGC GGN 1C2R 2C1R 3C 3C1R 3C2R 3C3R 3C4R
5 3GGC 2GGN 1C3R 2C2R 3C1R 4C 4C1R 4C2R 4C3R
6 4GGC 3GGN 1C4R 2C3R 3C2R 4C1R 5C 5C1R 5C2R
7 5GGC 4GGN 1C5R 2C4R 3C3R 4C2R 5C1R 6C 6C1R
8 6GGC 5GGN 1C6R 2C5R 3C4R 4C3R 5C2R 6C1R 7C

On the top row, find the relationship of one person to the common ancestor and follow the column straight down. Find the other person's relationship to the common ancestor on the left hand column and follow that row straight across. The relationship is where the projected row and column meet.

CA Common Ancestor
C Child
S Sibling
GC Grandchild
GGC Great-grandchild
N Niece/Nephew
GN Grand-niece/nephew
GGN Great-great-niece/nephew
#C Number of cousin (1C=1st cousin, 2C=2nd cousin, etc.)
#R Number of times removed (1R=once removed, 2R=twice removed, etc.)

NOTE: A first cousin once removed is a term that could describe either the child of your first cousin (in the descendancy) or the child of your great-aunt (in the ascendancy).

great great
great grandparent
great great
grandparent
great great
granduncle
grandaunt
great
grandparent
great
granduncle
grandaunt
1st cousin
thrice removed
grandparent granduncle
grandaunt
1st cousin
twice removed
2nd cousin
twice removed
parent uncle
aunt
1st cousin
once removed
2nd cousin
once removed
3rd cousin
once removed
SELF brother
sister
1st cousin 2nd cousin 3rd cousin 4th cousin
son
daughter
nephew
niece
1st cousin
once removed
2nd cousin
once removed
3rd cousin
once removed
grandson
granddaughter
grandnephew
grandniece
1st cousin
twice removed
2nd cousin
twice removed
3rd cousin
twice removed

great great
great grandparent
great great great
granduncle
grandaunt
1st cousin
five times removed
2nd cousin
five times removed
3rd cousin
five times removed
4th cousin
five times removed
great great
grandparent
great great
granduncle
grandaunt
1st cousin
four times removed
2nd cousin
four times removed
3rd cousin
four times removed
4th cousin
four times removed
great
grandparent
great
granduncle
grandaunt
1st cousin
thrice removed
2nd cousin
thrice removed
3rd cousin
thrice removed
4th cousin
thrice removed
grandparent granduncle
grandaunt
1st cousin
twice removed
2nd cousin
twice removed
3rd cousin
twice removed
4th cousin
twice removed
parent uncle
aunt
1st cousin
once removed
2nd cousin
once removed
3rd cousin
once removed
4th cousin
once removed
SELF brother
sister
1st cousin 2nd cousin 3rd cousin 4th cousin
son
daughter
nephew
niece
1st cousin
once removed
2nd cousin
once removed
3rd cousin
once removed
4th cousin
once removed
grandson
granddaughter
grandnephew
grandniece
1st cousin
twice removed
2nd cousin
twice removed
3rd cousin
twice removed
4th cousin
twice removed
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