What are they in relation to you?

1/22/2012 3:49:59 AM

Second cousin once removed.

[Edited on January 22, 2012 at 3:52 AM. Reason : didn't have to google. Still beat V that guy.]

1/22/2012 3:52:00 AM

2nd cousin once removed

[Edited on January 22, 2012 at 3:52 AM. Reason : found on google in about 5 seconds literally]

1/22/2012 3:52:11 AM

I wanted input from tdubbers

I never thought that "once removed" thing was an actual technical designation

1/22/2012 3:54:04 AM

I dunno, but don't bang her

1/22/2012 4:15:29 AM

once removed from whom?

1/22/2012 5:05:16 AM

it is indeed an actual technical designation

and the weirdest thing is that the same term is used for the reciprocal relationship, even though it's not symmetric

that is, the child of your second cousin is also your second cousin once removed, even though it's one generation down rather than up

it's as if the term "aunt" were additionally used for the same relationship that "niece" is now used for (in terms of cousin-ship, they're "zeroth cousins once removed" and if you allow your "negative-first cousin" to be yourself then anyone else can be related to you as an "nth cousin m-times removed" where n>-2 is an integer and m is a whole number)

1/22/2012 5:31:33 AM

i thought cousins were just how many steps up the family tree it takes to find a common descendant. your father's second cousin would be your third cousin?

[Edited on January 22, 2012 at 7:05 AM. Reason : also explains why you have like a million 4th, 5th, 6th cousins]

1/22/2012 7:04:35 AM

That's a common oversimplification, like some people think that "second cousin" means the same thing as "first cousin once removed."

To find out the degree and removal of cousinship, first determine the nearest common ancestor and note how many generations back they go (let's call them A and B); then each is the Nth cousin M-times removed of the other, where N is one less than the lesser of A and B (mathematically, N=min(A,B)-1) and M=|A-B|.

Typically, if M=0 then "0-times removed" is omitted, 0th cousins are referred to with terms like "sibling" (0th cousin 0-times removed) and "nephew" (0th cousin once removed, much like "uncle") and "great-aunt" (0th cousin twice removed, much like "grandniece") and -1st cousins are referred to with terms like "self" (-1st cousin 0-times removed) and "mother" (-1st cousin once removed, much like "daughter") and "grandson" (-1st cousin twice removed, much like "grandmother").


Anyway, you do indeed have many many third cousins and beyond, with very little consanguinity (less than four-fifths of 1%, assuming no further pedigree collapse): https://secure.wikimedia.org/wikipedia/en/wiki/Consanguinity
The typical level of consanguinity required to be sure a relationship is not classified as incestuous is less than 3.125%, the consanguinity of second cousins with no further pedigree collapse; however, in most Western countries and a few US states (including, oddly enough, ones that don't tend to go along with the rest of the West on, say, same-sex marriage), marriage between first cousins (12.5% consanguinity with no further pedigree collapse) is still legal.

That note about "no further pedigree collapse" is important, because a situation like double-cousinship (if two children from one set of parents each marry a different child from the same set of parents, the children from each marriage are called "double first cousins") causes the consanguinity to increase (in this case, to 25% with no further pedigree collapse, the consanguinity of half-siblings) and could lead to the invalidation of a marriage; however, North Carolina is the only state that allows marriage between first cousins but not double first cousins.

It turns out that starting at the level of 15th cousins with no further pedigree collapse (that is, the 16th generation of descent from a common ancestor), the average expected number of shared genes rounds to 0; given the typical age of parenthood, this would take more than 400 years.

Notably, this means that although the genealogical relationship between President Obama and Senator McCain is well-known (22nd cousin twice removed), the genetic similarity is probably the same as between any other two random people: http://www.wargs.com/political/om.html

1/22/2012 8:32:50 AM

People in the South often use a different set of rules for these designations. So if you're trying to talk to somebody about genealogy and stuff, you should double check the system they are using to make sure that they mean the same thing you do.

1/22/2012 9:33:32 AM

My father doesn't have a second cousin

1/22/2012 9:35:36 AM

1/22/2012 9:37:24 AM

http://www.wolframalpha.com/input/?i=father%27s+second+cousin+

1/22/2012 9:38:52 AM

^That's super cool!

1/22/2012 9:39:59 AM