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Family relationship

The family relationship between two individuals, where Ga and Gb are the number of generations between the individuals and their nearest common ancestor, can be calculated by the following:

x = min (Ga,Ga)
y = |Ga-Gb|
• If x=0 and y=0 then they are the same person.
• If x=0 and y=1 then they are parent and child.
• If x=0 and y=2 then they are grandparent and grandchild.
• If x=0 and y>2 then they are great ... great-grandparent and great ... great-grandchild, with y−2 greats.
• If x=1 and y=0 then they are siblings (brothers or sisters).
• If x=1 and y=1 then they are uncle/aunt and nephew/niece.
• If x=1 and y>1 then they are great ... great uncle/aunt and great ... great nephew/niece, with y−1 greats.
• If x>1 and y=0 then they are x−1th cousins.
• If x>1 and y>0 then they are x−1th cousins y times removed.

So two people sharing a pair of grandparents have x=2 and y=0 and are described as being first cousins.

If x>0 and they only share one nearest common ancestor rather than two, then the word "half" is sometimes added at the beginning of the relationship.

Last updated: 10-24-2004 05:10:45