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Cousin

descendant of an ancestor's sibling
A family tree showing how each person is related to the orange person.

In genealogy, a cousin is a relative, other than an ancestor or descendant, who shares a common ancestor. The word cousin is often used to refer to a person's first cousin - the child of someone's aunt or uncle.

How the cousin system worksEdit

  • A half-first cousin (a.k.a. half-cousin) is someone who shares the same one grandparent that your; the child of your half-aunt (parent's half-sister) or half-uncle (parent's half-brother); the half-nibling of your mother or father.
  • A first cousin (a.k.a. cousin) is someone who shares the same two grandparents (maternal or paternal) that you, but not either parent; the child of your aunt or uncle; the nibling of your mother or father.
  • A sesqui-first cousin (a.k.a. sesqui-cousin) is someone who shares the same three grandparents that you; the child of your maternal aunt (mother's sister) with your paternal half-uncle (father's half-brother), or the child of your paternal aunt (father's sister) with your maternal half-uncle (mother's half-brother), or the child of your maternal half-aunt (mother's half-sister) with your paternal uncle (father's brother) or the child of your paternal half-aunt (father's half-sister) with your maternal uncle (mother's brother).
  • A double-first cousin (a.k.a. double-cousin) is someone who shares the same four grandparents that you; the child of your maternal aunt (mother's sister) with your paternal uncle (father's brother) or the child of your paternal aunt (father's sister) with your maternal uncle (mother's brother); the nibling of blood of your mother and of your father at the same time.
  • A half-second cousins are the children of their parent's half-first cousins. Half-second cousins share one great-grandparent.
  • A second cousin relationship with the children of their parent's first cousins. Second cousins share two great-grandparents.
  • A sesqui-second cousins are the children of their parent's sesqui-first cousins or are the children of their parent’s half-first cousin with their other parent’s first cousin. Sesqui-second cousins share three great-grandparents.
  • A double-second cousins are the children of their parent's double-first cousins are the children of their parent’s first cousin with their other parent’s first cousin. Double-second cousins share four great-grandparents.
  • A 2.5-tuple-second cousins are the children of their parent’s first cousin with their other parent’s sesqui-first cousin or are the children of their parent’s double-first cousin with their other parent’s half-first cousin. 2.5-tuple-second cousins share five great-grandparents.
  • A triple-second cousins are the children of their parent’s double-first cousin with their other parent’s first cousin or are the children of their parent’s sesqui-first cousin with their other parent’s sesqui-first cousin. Triple-second cousins share six great-grandparents.
  • A 3.5-tuple-second cousins are the children of their parent’s double-first cousin with their other parent’s sesqui-first cousin. 3.5-tuple-second cousins share seven great-grandparents.
  • A quadruple-second cousins are the children of their mother’s double-first cousin with their father’s double-first cousin. Quadruple-second cousins share eight great-grandparents.
  • A third cousin is someone who shares the same two great-great-grandparents that you, but not parents, grandparents or great-grandparents.
  • A forth cousin is someone who shares the same two great-great-great-grandparents that you, but not parents, grandparents, great-grandparents or great-great-grandparents.

etc.

A cousins-aunts and cousins-uncles are:

  1. The cousins of parents.

A cousins-nieces and cousins-nephews are:

  1. The children of cousins.

A great-cousins-aunts and great-cousins-uncles are:

  1. The cousins of grandparents.

A great-cousins-nieces and great-cousins-nephews are:

  1. The grandchildren of cousins.

A second cousins-aunts and second cousins-uncles are:

  1. The second cousins of parents.

A second cousins-nieces and second cousins-nephews are:

  1. The children of second cousins.

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