Cousin

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Commonly "cousin" refers to a "first cousin" or equivalently "full cousin". First cousins are people whose most recent common ancestor is a grandparent.[1] This relationship was also called cousin-german in the past.[citation needed]

More generally, cousin is a type of familial relationship in which people with a known common ancestor are both two or more generations away from their most recent common ancestor. This distinguishes a cousin from an ancestor, descendant, sibling, aunt, uncle, niece, or nephew.[2]

Systems of "degrees" and "removals" are used in the English-speaking world to describe the exact relationship between two cousins (in the broad sense) and the ancestor they have in common.[3] Various governmental entities have established systems for legal use that can precisely specify kinship with common ancestors any number of generations in the past.[citation needed] Common usage often eliminates the degrees and removals, and refers to people with common ancestry as simply "distant cousins" or "relatives".[4]

Basic definitions[edit]

Family tree. Cousins are colored green. Generations are shown by alternating stripes of gray and white.

People are related with a type of cousin relationship if they share a common ancestor and the most recent common ancestor is two or more generations away from both people. This means neither person is an ancestor of the other, they do not share a parent (siblings), and neither is a sibling of a common ancestor (aunts/uncles and nieces/nephews).[2]

The cousin relationship is further detailed by degree and removal. For example the second cousin once removed relationship is a second-degree cousin with one removal.

The removal of the cousin relationship is the number of generations the cousins are apart. When the cousins are separated by a different number of generations from the most recent common ancestor, the cousin relationship is removed. The difference between the number of generations for each cousin is the removal.[3] For example if the most recent common ancestor is 2 generations prior for one person and 3 generations prior for the other (one person's grandfather is the other person's great-grandfather) or the most recent common ancestor is 3 generations prior for one person and 4 generations prior for the other (one person's great-grandfather is the other person's great-great-grandfather) the cousins are separated by one generation and therefore once removed. Note that two people can be removed but be around the same age due to differences in birth dates of parents children and other relevant ancestors.[3][5]

The degree of the cousin relationship is the number of generations prior to the parents before a most recent common ancestor is found. If the cousins are removed, the smaller number of generations to the most recent common ancestor is used to determine the degree of the cousin relationship.[3] For example if one of the cousins has to go back one generation beyond their parents (the grandparents) before finding the most recent common ancestor and the other has to go back one or more they are first cousins. If one had to go back two generations beyond the parents (great grandparents) and the other had to go back two or more they would be second cousins[5][3].

Examples[edit]

Example family tree
Jason Beatrice
James Helen Eugene Mary
Nancy Joseph Julie Roger
Gordon Laura Christina Matt
Sam Lyla
First cousins
A person shares a first cousin or cousin relationship with the children of their parents' siblings. Cousins share at least one set of grandparents.[5] In the example family tree, Joseph and Julie are first cousins.
Second cousins
A person shares a second cousin relationship with the children of their parents' cousins. Second cousins share at least one set of great-grandparents.[5] In the example family tree, Gordon and Matt are second cousins.
Third cousins
A person shares a third cousin relationship with the children of their parents' second cousins. Third cousins share at least one set of great-great-grandparents.[5] In the example family tree, Sam and Lyla are third cousins.
First cousins once removed
A person shares a first cousins once removed relationship with their parents' cousins and their cousins' children. At least one set of one person's grandparents are the great-grandparents of the other person.[5] In the example family tree, Gordon and Julie, as well as Joseph and Matt, are first cousins once removed.
First cousins twice removed
A person shares a first cousins twice removed relationship with their grandparents' cousins and their cousins' grandchildren. At least one set of one person's grandparents are the great-great-grandparents of the other person.[5] In the example family tree, Sam and Julie, as well as Joseph and Lyla, are first cousins twice removed.
Second cousins once removed
A person shares a second cousin once removed relationship with their parents' second cousins and their second cousins' children. At least one set of one person's great-grandparents are the great-great-grandparents of the other person.[5] In the example family tree, Sam and Matt, as well as Gordon and Lyla, are second cousins once removed.

Relationship charts[edit]

A "table of consanguinity", is helpful in identifying the degree of cousin relationship between two people using their most recent common ancestor as the reference point. Cousinship between two people can be specifically described in degrees and removals by determining how close, generationally, the common ancestor is to each person.[6][3][5]

If the relative's → Parent Grandparent Great-grandparent Great-great-grandparent Great-great-great-grandparent Great-great-great-great-grandparent
Is the subject's
Then the relative is the subject's ↘
Parent Sibling Niece/​Nephew (Nibling) Grandnephew/​Grandniece Great-grandnephew/​Great-grandniece Great-great-grandnephew/​Great-great-grandniece Great-great-great-grandnephew/​Great-great-great-grandniece
Grandparent Uncle/​Aunt 1st cousins 1st cousins once removed 1st cousins twice removed 1st cousins three times removed 1st cousins four times removed
Great-grandparent Granduncle/​Grandaunt 1st cousins once removed 2nd cousins 2nd cousins once removed 2nd cousins twice removed 2nd cousins three times removed
Great-great-grandparent Great-granduncle/​Great-grandaunt 1st cousins twice removed 2nd cousins once removed 3rd cousins 3rd cousins once removed 3rd cousins twice removed
Great-great-great-grandparent Great-great-granduncle/​Great-great-grandaunt 1st cousins three times removed 2nd cousins twice removed 3rd cousins once removed 4th cousins 4th cousins once removed
Great-great-great-great-grandparent Great-great-great-granduncle/​Great-great-great-grandaunt 1st cousins four times removed 2nd cousins three times removed 3rd cousins twice removed 4th cousins once removed 5th cousins
Canon Law Relationship Chart. See an example of how to use chart.

Another visual chart used in determining the legal relationship between two people who share a common ancestor is a "canon law relationship chart".

The chart is the same as the previous chart with the exception that the chart is symmetrical and has been rotated 45° so that the common progenitor (most recent common ancestor) is placed at the peak. Since the graph is symmetrical the placement of either party in the realationship on either side of the graph is arbitrary. The graph does not distinguish between parents and children, or aunts/uncles and nieces/nephews. For these non symmetrical relationships the relationship of the person from the most recent generation is displayed (I.e. children and nieces/nephews).

Cousin marriage[edit]

Cousin marriage is important in several anthropological theories which often differentiate between matriarchal and patriarchal parallel and cross cousins. A parallel cousin is a cousin from a parent's same-sex sibling, while a cross cousin is from a parent's opposite-sex sibling.

Currently about 10% and historically as high as 80% of all marriages are between first or second cousins.[7][8] Cousin marriages are often arranged.[7][8][9][10][11] Anthropologists believe it is used as a tool to strengthen the family, conserve its wealth, protect its cultural heritage, and retain the power structure of the family and its place in the community. Some groups encourage cousin marriage while others attach a strong social stigma to it. In some regions in the Middle East over half of all marriages are between first and second cousins. Some of the countries in this region this may exceed 70%.[12] Just outside this region it is often legal but infrequent. In other places it is legally prohibited and culturaly equivalent to incest[13][14] Supporters of cousin marriage often view the prohibition as discrimination,[15][16] while opponents cite the potential immorality.[17]

Married couples that possess higher than normal consanguinity, shared identical DNA and genetic material, have an increased chance of sharing genes for recessive traits. The percentage of consanguinity between any two individuals decreases fourfold as the most recent common ancestor recedes one generation. First cousins have four times the consanguinity of second cousins, while first cousins once removed have half that of first cousins. Double-first cousins have twice that of first cousins and are as related as half-siblings. Children of these marriages may have an increased risk of genetic disorders, particularly if their parents both carry a harmful recessive mutation.[citation needed]

Additional terms[edit]

The following is a list of less common cousin terms.

Term Definition Example Chart
Double cousin Double cousins arise when two siblings of one family mate with two siblings of another family. The resulting children are related to each other through both of their parents and are thus doubly related. Double first cousins share both sets of grandparents and have twice the degree of consanguinity of ordinary first cousins; genetically, they are as related as half-siblings. In a scenario where two monozygotic (identical) twins mate with another pair of monozygotic twins, the resulting double cousins would test as genetically similar as brothers or sisters. Double second cousins can arise in two ways: from the relationships of two first-cousins with two other first-cousins or from the relationships two double-first-cousins with two other persons. May also be known as 'Cousins on both sides.' Joseph and Julie are double first cousins because each is related through their mother's family and also their father's family, the result of a brother and sister (Helen and Eugene) having married another brother and sister (James and Mary). For Joseph and Julie, each has a mother who is an aunt by blood of the other and a father who is an uncle by blood of the other.
Gary Glenda
Jason Beatrice
James Helen Eugene Mary
Joseph Julie
Half-cousin Half-cousins are the children of two half-siblings, and their respective spouses. Joseph and Lilian are half cousins because their parents (Helen and Charles) are half-siblings, their grandmother (Beatrice) having remarried.
Jason Beatrice Anthony
James Helen Charles Janet
Joseph Lilian
Stepcousin Stepcousins are either stepchildren of an individual's aunt or uncle or nieces and nephews of one's stepparent. Joseph and Rachel are stepcousins because Joseph's uncle (Eugene) has become Rachel's stepfather as a result of Rachel's mother (Corinda) having remarried Eugene.
Jason Beatrice
James Helen Eugene Corinda Colin
Joseph Rachel
Cousin-in-law A cousin-in-law is the spouse of an individual's cousin or the cousin of one's spouse. Joseph and Roger are first cousins-in-law to each other because Roger's wife (Julie) is Joseph's first cousin.
Jason Beatrice
James Helen Eugene Mary
Joseph Julie Roger
Maternal or paternal cousin A term that specifies whether one individual is a cousin of another through the mother's side of the family (maternal) or the father's side (paternal). If the relationship is not equally paternal for both or equally maternal for both, then the paternal cousin of one is the maternal cousin of the other. Julie and Natalia are maternal first cousins (being related through their mothers). Julie is also Joseph's maternal first cousin (as related on Joseph's mother's side), but Joseph is Julie's paternal first cousin (as related on Julie's fathers's side). Joseph and Natalia would only be related if they shared a common ancestor.
Jason Beatrice Gary Glenda
James Helen Eugene Mary Maud Mark
Joseph Julie Natalia

See also[edit]

References[edit]

  1. ^ "Cousin". Brewer's Dictionary of Phrase & Fable. Chambers Harrap Publishers. 2013. 19. 
  2. ^ a b "Definition of Cousin by Merriam-Webster". merriam-webster.com. Merriam-Webster. 
  3. ^ a b c d e f A Dictionary of Genetics. Oxford University Press. 2013. 8. 
  4. ^ "Definition of cousin in English by Oxford Dictionaries". oxforddictionaries.com. Oxford University Press. 
  5. ^ a b c d e f g h i "Genetic And Quantitative Aspects Of Genealogy – Types Of Collateral Relationships". Genetic-genealogy.co.uk. Retrieved 28 October 2014. 
  6. ^ "What is a First Cousin, Twice Removed?". Genealogy.com. Retrieved Sep 26, 2015. 
  7. ^ a b Kershaw, Sarah (26 November 2009). "Shaking Off the Shame". The New York Times. 
  8. ^ a b Richard Conniff. "Go Ahead, Kiss Your Cousin."
  9. ^ Bittles, Alan H. (May 2001). A Background Summary of Consanguineous Marriage (PDF) (Technical report). Edith Cowan University. 
  10. ^ Bittles 1994, p. 567
  11. ^ Bittles and Black 2009, Section 7
  12. ^ Dr. Alan Bittles; Dr. Michael Black. "Global prevalence". consang.net. 
  13. ^ The Surprising Truth About Cousins And Marriage
  14. ^ Diane B. Paul and Hamish G. Spencer. "It's Ok, We're Not Cousins by Blood."
  15. ^ "Final Thoughts". Cousin Couples. Retrieved 4 June 2016. 
  16. ^ Brandon Keim (23 December 2008). "Cousin Marriage OK by Science". Wired. 
  17. ^ The Love That Dare Not Speak Its Surname: What's wrong with marrying your cousin?

External links[edit]