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Pastimes : Genealogy
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To: ManyMoose who wrote (375)8/28/2010 10:19:13 PM
From: goldworldnet  Read Replies (1) of 443
 
Cousin Tree



Double cousins

Double first cousins arise when two siblings of one family reproduce with two siblings of another family. The resulting children are related to each other through both parents' families. Double first cousins share both sets of grandparents in common and have double the degree of consanguinity than ordinary first cousins. Genetically, they are as related as half-siblings, sharing 25% of their DNA (a coefficient of relationship of 1/4).[2] Their coefficient of coancestry is 1/8th or 0.125. While double first cousins have the same coefficient of coancestry (1/8) as half-siblings, they do have higher chances of sharing both alleles (1/16 vs 0) and lower chances of sharing one allele (3/8 vs 1/2) with each other than half-siblings.

When identical twins reproduce with a pair of siblings, the resulting children are more related than half-siblings but less related than full siblings (they are genetically equivalent to 3/4 siblings) although they are legally double first cousins.
When identical twins reproduce with another set of identical twins (sometimes called quaternary marriage), the resulting children are likewise genetically indistinguishable from full siblings, although they are genealogically double first cousins.

Double cousin marriage is specifically prohibited in the US state of North Carolina (N.C. Gen. Stat. § 51-3). It is permitted in the other 25 states that permit marriage between first cousins.[3]

en.wikipedia.org

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