90.1 Two questions today from the mailbag fit together nicely. But first, let me give you a list of relatives: mother/father, son/daughter, brother/sister, uncle/aunt, nephew/niece, grandfather/grandmother, grandson/granddaughter, great grandparent/great grandchild, and cousin…which is to say, 1st cousin, offspring of your parent’s sibling. These form the basic core of our kinship terms and relationships…we learn them early on in life, and our understanding of them is rock solid.
90.2 When we move beyond them, many people get confused…and when I say “move beyond,” I simply mean using these relationships as compounds…building upon the basics, like this: father’s uncle, father’s cousin, cousin’s son, etc. When I listed those terms in 90.1, you probably thought of them as how they applied to you…they are the people most closely related to you. But your father has all these relatives too, and because he’s your father, they are all related to you as well…but how? Thus our first question…
Dear Stolf: What is the best way to explain how you are related to your 2nd cousin…so that others can understand it…and I can understand it myself? …from Sparky, Sebastopol, CA
90.3 Dear Sparky: Good Grief! Excellent question. There are 3 basic definitions…all work, all are correct, but not all are equally clear…and you’re looking for the easiest to understand, nez pah? The Grandparent Definition is the worst, because it’s the hardest to understand…the Cousin Definition is the best because it’s the easiest to understand…finally, the Sibling Definition is also a good way, it’s a bit more complicated than the Cousin Definition…but only a bit more. We’ll examine each of these in turn.
90.4 Grandparent Definition of Cousins (GDC)
1st cousins share a common grandparent
2nd cousins share a common great grandparent
3rd cousins share a common great great grandparent
This is the most frequent way you will find Numbered Cousins defined…and it’s really a diservice, because taken literally, just as they are stated above, these rules fail in 2 different ways…and for them to be correct, they must be modified to the point where they become very convoluted and confusing. True, once modified, they are completely correct and very understandable, if you take the time to note all the qualifications. In this way, the GDC becomes trustworthy, but unnecessarily cumbersome.
90.5 First way they fail: by the above definitions, your siblings are your 1st cousins, since you share with your siblings a common grandparent, right? Likewise, your siblings and 1st cousins are also your 2nd cousins…and your siblings, 1st cousins, and 2nd cousins all qualify as your 3rd cousins…which in each of these cases simply isn’t true. First modification, using the rule for 1st cousins as an example…share a grandparent as the closest common ancestor. Now while it’s true that you and your sibling have a common grandparent, that ancestor is not your closest common ancestor…your parent is. Thus, thankfully, you and your sibling are not 1st cousins. And this modification applies right down the line, to 2nd cousins, 3rd cousins, etc…
90.6 Second way they fail: Half-first cousins also share a grandparent as their closest common ancestor. But half-1st cousins are not 1st cousins…they share only 1/16 of their genes, while 1st cousins share 1/8. Half-1st cousins have the same grandfather, but different grandmothers…that grandfather had 2 different families with 2 different women. So the second modification could be: …share 2 grandparents as the closest common ancestors. What we’re shooting for is shown above in Chart 312a. But this still doesn’t work, because you could be double half-cousins…that is, half-cousins on your father’s side and on your mother’s side…as in Chart 312b, you share 2 grandfathers and no grandmothers. OK then, make it …share a grandfather and a grandmother as the closest common ancestors. Again, this won’t do it, since as in Chart 312c, you could do that, have “one of each,” and still be double half-cousins, not full 1st cousins.
90.7 It should be obvious that what we really need is for you to share the same married pair of grandparents…but how do we say that succinctly, considering that they may not be married, just had children together? I’m going to stop here…as you can imagine, putting all this together does work, but it’s messy. If that were the only way to define Numbered Cousins, we’d be stuck with it…fortunately, it isn’t and we’re not…
90.8 Cousin Definition of Cousins (CDC)
1st cousins are the offspring of siblings
2nd cousins are the offspring of 1st cousins
3rd cousins are the offspring of 2nd cousins
Done and done…iron-clad and airtight. Notice that all the fuss about how many grandparents and precisely which ones is unequivocally decided by that one word “siblings.” Siblings are not half-siblings…siblings have the same father and the same mother…married, unmarried, doesn’t matter. Half-‘s are ruled out by definition…and going along, “offspring of 1st cousins” does the trick for defining 2nd cousins, “2nd cousins” for 3rd cousins, etc. (And if you’re of a truly mathematical bent, “siblings” can be replaced by “0th cousins…making it a definition derived only from cousins.)
90.9 OK, given people’s extraordinary ability to misunderstand even the simplest declarative sentence, you might suspect there is one tiny leak. But not really. I daresay 99.99% of the people reading the above CDC realize that the siblings who have the offspring who are 1st cousins, these siblings are not married to, or procreating with, each other. In the normal course of events, 2 brothers marry 2 women…these women are not related to each other, or to the brothers. But what if they were? Let’s take the worst case, and say you and I are back in ancient Egypt, and our parents are indeed brother and sister. We are siblings…we are also 1st cousins..in fact, double 1st cousins…that is, 1st cousins in 2 different ways, since my father is the sibling of your mother, and my mother is the sibling of your father. Fine, but the CDC rule still holds…it’s just that, besides being 1st cousins, we are also something else. But we are nevertheless 1st cousins. Now let’s take the CDC back one generation…
90.10 Sibling Definition of Cousins (SDC)
1st cousins have parents who are siblings
2nd cousins have grandparents who are siblings
3rd cousins have great grandparents who are siblings
Once again, the word “siblings”…now used to define each degree of Numbered Cousins…specifies 2 people who have the same father and the same mother…no half-‘s included. And even if those siblings are procreating with each other, the definition still holds…it’s just that there will now be other ways the cousins are related besides what the definition says, as showed by our Egyptian example. Really, between the CDC and the SDC there is very little to choose…both absolutely nail the Numbered Cousin relationships…in some cases, one might be more useful in seeing the actual cousin connection than the other. Personally, I find the CDC a little clearer, that’s all…but not by much!
90.11 Then again, if you want to complicate it, nobody’s stopping you…this then would be the equivalent of the SDC as stated above…still correct, just more wordy…and I wonder why you would feel the need to go both up and down the family tree…when simply going up will do the trick quite nicely, thank you…
my 1st cousin is the child of my parent’s sibling
my 2nd cousin is the grandchild of my grandparent’s sibling
my 3rd cousin in the great grandchild of my great grandparent’s sibling
Dear Stolf: I’m having an on-going argument with my brother. Can you have 2nd cousins without having 1st cousins? He says no way…I say of course way. Can you please help us? …from Sissy in Siblingburg
90.12 Yes, I can settle your squabble, which I hope hasn’t escalated to the point of one of you saying to the other: “Oh yeah? Well you were adopted!” But what I really like about your question is it gives me a chance to show how the above SDC can be preferable to the CDC. Look at SDC, and suppose your mother is an only child, and so is your father. You have no 1st cousins, since neither of your parents have siblings. But does that prevent your grandparents from having siblings? Of course not! Or your great grandparents? Ditto. So you could have 2nd cousins, and 3rd cousins, and on down the line. It’s just that simple.
90.13 Now it’s true you can draw the same conclusion from the CDC. The trouble is, it’s a little less obvious. If your parents have no siblings, you have no 1st cousins…and the 2nd cousin rule states: 2nd cousins are the offspring of 1st cousins. What you must realize is, since we’re talking about your 2nd cousins, “offspring of 1st cousins” doesn’t mean your 1st cousins…and anyway, we already know you don’t have any…it means your parent’s 1st cousins! And the only way your parent can have a 1st cousin is if your grandparent has a sibling, so we’re back to the SDC. See how it all ties together? Pretty cool, sez me.
90.14 BTW…Anyone who incorrectly thinks that your 2nd cousin is the child of your 1st cousin…would naturally conclude that without any 1st cousins, 2nd cousins aren’t possible. A valid argument, but an invalid conclusion nonetheless, because it’s based on a premise that is false. And anyway, it would only mean that you as 1C1R ascending wouldn’t have a 1C1R descending. But you yourself could be the 1C1R descending, and you could then have a 1C1R ascending…that is, your parent’s 1st cousin, which you would incorrectly…but at least if you’re being consistent…have to call your 2nd cousin…since you are his 2nd cousin in the sense of being the child of his 1st cousin. Perhaps that’s what was in your brother’s head…either way, you’re right, he’s wrong…as Archie Bunker would say, ipso fatso. See yez next week…
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