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Comment by roninb | Hacker News Reader

In case you were also wondering what a "fourth cousin" was, someone who shares a pair of great-great-great grandparents[0]. Wikipedia has a great set of diagrams[1] in case you're also confused about first, second, or third cousins. I figure through induction you can presume any nth and nth removed from that page (I foolishly thought 3rd was where people arbitrarily stopped keeping count....)

[0] https://www.reference.com/family/fourth-cousin-7b40e096c6d65...

[1] https://en.wikipedia.org/wiki/Cousin#First_cousins

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I get mad at people who think sons of first-cousins are second-cousins all the time -- and, frankly, almost everyone I know think this way.

I'm glad you linked to this Wikipedia article that proves I'm not mad into thinking there is a simple logic pattern that can be applied to cousinship.

However, this "once removed" notation is crazy. Why not second-uncle for parents of second-cousins and so on?

Pardon me for my ignorance, but wouldn't sons of first cousins be second cousins?

Language quirk :) The son of my first cousin is my first cousin once removed. My son and my cousin's son are second cousins.

Ah, I read "sons of first cousins" as "two people who are first cousins to each other each have a son". "A son of a first cousin" would be much less ambiguous. In fact, even knowing what you meant, I have a hard time reading the meaning you intended to convey.

Another clearer way to phrase it would be "sons of my first cousin are not my second cousins".

Actually the term "second cousin" does not have a concrete meaning. It can mean a true second cousin, or it can also mean a generation removed from a first cousin. The "once removed" terminology was introduced to compensate for this ambiguity.

No! Stop the removed madness!

Generally the "1st/2nd" bit denotes how many generations up you have to go to find a common ancestor, and "removed" is how many generations removed the other person is from that generation.

You are, to your your first cousin's child, who is your first cousin once-removed, a second cousin once-removed.

yes. the wording and the fact that other people seemed to agree with the op made me spend way too much time on this.

He must be referring to one's own first cousin's children. Not the children of two first cousins.

You can call them anything you like, I'm just saying that you shouldn't.

There's an app for that!

https://www.microsoft.com/en-us/store/apps/cousinosity/9nblg...

That's what I use.

2nd uncle, 2nd grand aunt

Fun fact: in Russian a first cousin is a 2nd Brother/Sister, a 2nd cousin is a 3rd Brother/Sister and so on.

That makes a lot of sense! The distinction between sibling and nth cousin is basically arbitrary. (Although obviously there is logic in making the distinction as well as in omitting it.)

Arbitrary? You have the same parents with sibling; with cousin you share only one of the two pairs of grandparents.

Actually that's often but not always true -

    brother b1 and sister s1 from family 1, with parents g1
    brother b2 and sister s2 from family 2, with parents g2
    s1 has child x with b2 - x has grandparents g1, g2
    s2 has child y with b1 - y has grandparents g1, g2

x and y are cousins, and also share the same 2 pairs of grandparents :-)

Those are "double first cousins". I even have some triple cousins in my tree, where three siblings from one family married three siblings from another family.

It can get even more fun!

If instead of two brothers marrying two sisters, you have two brothers marrying two first cousins, like so...

    b1 and b2 are brothers
    c1 and c2 are first cousins
    b1 and c1 marry and have child x
    b2 and c2 marry and have child y

... then x and y are both first and second cousins (and their children are second + third cousins, etc).

Agreed: in the case of siblings you share all ancestors; with cousins only some. In that way the distinction makes sense. The other way to look at it though is that with siblings your common ancestor is one generation up. With first cousins, it's two. With second, it's three. So it's the same thing, just a matter of degree.

No, you don't. You don't call a son of your first-cousin your second-cousin. You call him a second nephew I think.

First cousin once removed.

https://upload.wikimedia.org/wikipedia/commons/4/4c/Cousin_t...

No, stop that removed madness!

Thank you for being sane.

Russians are decent people, it seems. Is the 2nd-uncle terminology widespread in Russia too?

Also good because it means you are your own 0th brother which makes sense. In the western version you are your own -1st cousin :(

Edit: Nvm. I am more confused than I thought.

I've always wondered about this one:

My father's first-cousin-once-removed is what to me?

That depends on which direction the cousin is removed. If a generation above your father, it is your first cousin twice removed. If a generation below, it is your second cousin.

Your second cousin if you share the same great-grandparents.

Edit: Ugh, this gets confusing. I was mistaken. I'd originally included the once-removed, but that appears to be incorrect. Or I'm still mistaken. :)

A first cousin once-removed signifies one person's grandparent is the other's great-grandparent.

Perhaps this cousin chart would help: https://en.m.wikipedia.org/wiki/Cousin#Relationship_charts

Just plot yourself and the cousin-in-question by where your shared nth-grandparent lies.

Depends on the direction removed?

I think, if your father's cousin-once-removed is a generation below him, then he/she is your first-cousin. While a generate above you father would signal first-cousin-twice-removed...

Thoughts?

In the first case he/she would be your second cousin, not first.

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

First cousin twice removed, apparently.

You are a (1,0)-child to your father (who is a (0,1)-parent to you). Your father is either (2,3)-cousin or (3,2)-cousin to the other person. It is ambiguous from the terminology. So you are either (3,3)-cousin or (4,2)-cousin to them. That is second cousin for the former and first cousin twice removed for the latter.

You are hitting the borders where logic and common usage meet.

I am actually surprised that descriptive grammar holds up so well to logic. (There's no a priori reason why descriptive grammar, that describes common usage of language, actually is as mostly compressible to simple rules as it is.)

If there's a clearer and more specific way to speak about something, we should try to use it.

Design of language is a constant trade-off, between ease of remembering, compression (ie giving shorter ways to express more common concepts), fault-tolerance, desire of the speaker to look clever, fashion, ...

And all of us work on the evolution of language every day.

You get mad? Really? Why?

Worse even, the "once removed" notation has no notion of direction, so it's inherently ambiguous. I'm also pretty sure that less half of the people I hear using it know what it means (or tries to mean).

This got me confused. You actually mean people who confuse "second niece" (i.e. your cousin's son) with "second cousin". Is that usage common in english? The daughters of cousins are second cousins,no?

That's how we've always done it.

* Brother of father is uncle. Son of uncle is cousin. Son of son of uncle is second cousin.

* Brother of grandfather is great-uncle. Son of great-uncle is second cousin.

That's exactly what you shouldn't be doing.

Isn't the term "uncle" relatively recent? I recall Hamlet referring to his father's brother as his cousin.

You must be very old.

Where our family is from the priests wouldn't allow marriage between 6th cousins. My grandfather was 6th cousins three times removed from my grandmother. (so she was 9 generations away from common ancestors with him) They had to get written permission from the bishop to get married.

Sounds like they basically penalized record keeping ...

Ah, it was probably the Church who was keeping the records in the first place.

The beauty of selective enforcement. Dig deep enough into your ecclesiastical data-monopoly and you can veto just about any marriage at will. It never was the same again once laymen started to read and write.

Yes, it was the Franciscans who were a huge influence and kept record of these things.

Most people would remember relations as far as great-grandparents and relations to families/family friends that they knew. Literacy was pretty high in the region early on as well, but people continued to rely on the church for recordkeeping.

The Church worked very deliberately over centuries to reduce the influence of families / clans, in some places more successfully than others. It all revolves around inheritance rights and accumulated power. (Also in some cases the Church could collect money by charging for exemptions.)

https://en.wikipedia.org/wiki/Consanguinity#Religious_and_tr...

Through induction, you can also say that your sibling is your nilth (0th) cousin, and your identical twin is your negative-first cousin. That makes aunt or uncle a nilth cousin once removed, and a great aunt or great uncle a nilth cousin twice removed. Your parents are negative-first cousins once removed.

If this sounds ridiculous, that's because it is, as a natural consequence of the ridiculous nomenclature.

It would be far less confusing to just insert an unordered pair of numbers for both individuals' genetic distance from their common ancestor. So instead of a first cousin once removed, you would have a (2,3)-cousin. Identical twins would be (0,0), parents would be (0,1), ordinary siblings (1,1), aunts and uncles (1,2), and so on. A fourth cousin would be (5,5).

But that doesn't account for half-siblings, so it would be inadequate for some family relationships.

I used to really struggle with those types of diagrams. Like, they make sense on their own, but it's hard to reason about the patterns with them; the relationships (heh) between each diagram aren't clear.

I much prefer the square/diamond type diagram that's further down in the article. It seems like black magic at first, but if you stop and think about it for a bit, once you understand it, is crystal clear.

I guess it's about short-term or long-term ease of understanding.

Let's calculate. I have a pair parents, 2 pairs grandparents, 4 pairs of great grandparents, 8 pairs great-great grandparents, and 16 pairs great-great-great grandparents.

How to estimate the number of fourth cousins?

Wow, takes me way back to an undergrad programming assignment to take a family tree and compute the degree and "removedness" of any two cousins.

It is mentioned in some comments of comments further down but Wolfram Alpha has some great family tree generation.

http://www.wolframalpha.com/input/?i=fourth+cousin

Also, its grand-uncle (not great-uncle). You don't have a great-mother do you? Its a grandmother. Thus granduncle.

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