What do you call this familial relationship?

Factual Questions
61

I should mention that IANA geneticist or anything. The subject fascinates me though and I’ve studied on it some. After long consideration, I say no.

First, by definition “siblings” must have at least one parent in common. By the third child, it’s the deceased father’s brother having a child with the deceased mother’s sister. The children would be blood relatives of course, but not siblings because there’s no common parent.

Setting that technicality aside, are they related enough to be quarter siblings? Actually I think they’re related too much. My (full) siblings and I have 50% of the same DNA. I got one half from my dad…my brother maybe got a similar but different set.

And so it is with the father’s brother and mother’s sister, whom the example crosses at the end. In the 3/4 sib example, father’s brother substituted when he died, making future children 25% on paternal side but still 50% on maternal side. This would make it 25% + 25% =50%. Your uncle’s and aunt’s child at the end would be as related to you as much as half-siblings, not quarter. So I think if you make that second remarriage to a stranger, that would hit the number.

I think I have determined that quarter siblings is an impossibility. When you have full siblings, there are two shared parents and four shared grandparents. If you have half siblings, one parent is common (as well as two shared grandparents). So it would seem like if you could engineer a scenario where only one grandparent is shared, that could give you a quarter sibling.

So Adam marries Betty and they have a son, Charles.
They divorce.
Adam marries Donna and they have a son, Edward.
Charles and Edward are half siblings. Their children would have one common grandparent. But those kids would be half cousins.

Short story long, if siblings must have one parent in common, they will always have that parent’s two parents in common—as few as two common grandparents, but never one.

Yes, I think I’d read something about them long ago. One image that has stuck with me for a long time—remember seeing the inbred girl through the window in the film “Deliverance?” Sad, sad stuff.

I hope we’ve answered OP’s question and this won’t be too much of a hijack.

I was thinking about a book I read once that talked about inbreeding in mice. I took it to mean that for whatever reason, they don’t circulate enough. So I searched. First I found that they breed brother/sister mice 20 times…yes, on purpose. I guess they’re hoping for identical mice so they can any change in condition must be due to the experimental treatment, etc. Wow, I have a lot of conflicting feelings about some of the material in the article.

A few years ago, a big nonprofit mouse breeding facility in Bar Harbor, Maine, went up in flames. 400,000 mice died. Ordinary mice and valuable special strains. More than 1,700 different kinds of mice. A colossal blow to the medical research establishment.

Lots of sentence fragments ahead but he seems to know what he’s talking about.

62

Could I ask that we leave this out of this GQ thread? There are many other threads about this. I am asking about genealogy and biology (or adoption which substitutes for this biology). I don’t care what people want to call themselves. I consider my best friend my “brother” but he is not my brother. Could I respectfully ask that we stay within the parameters of the GQ asked?

63

Then i will reiterate that in English, it’s common to call people “brothers” if they are both children in the same household and share parents. So i think this is the factual answer: “in English, there is no special term for this relationship, but they would likely be referred to as brothers”

64

They don’t “share parents” in my GQ unless you are delving into the things I requested that you not go into. :slight_smile:

65

Yeah, O.P. I think this is as close to an answer as you’re gonna get.

There may be specific terms for this relationship in other languages, but as this is an English-language message board, that’s the best we can do.

66

Is the elder one still living with his father? Even if he hasn’t been formally adopted by his aunt/stepmother, she is his parent. I know you are more concerned with the biology than the relationship, but i don’t think English relationship-names reflect your preference.

As another example, your mother’s brother and your mother’s sister’s husband are both called your uncle. One is a close blood relative and the other may be completely unrelated to you. But English doesn’t distinguish.

I believe there are other languages that do distinguish. (There are also languages that distinguish between your mother’s brother and your father’s brother.)

67

Full brothers are zeroth cousins. (ETA: I see now that Chronos ninjaed on this point.)

I saw a chart once that listed all kinds of relationships as kinds of cousins. Your nephew, for example, is your zeroth cousin once removed (I think).

68

And extending it yet further, you are your own negative-oneth cousin. And your parents, having an ancestor of degree negative one in common, are negative-second-cousins.

As for “1/4 sibling”, if you just want something that has the right degree of relationship, ordinary first cousins would do it.

69

Yes, assume he is. That really doesn’t make her a parent. Say a divorced woman with primary custody of a child moves in with a man. Does that make him a father, even if the child’s biological father is living and gets the child every other weekend? What if she stays a few nights per week?

To your second point, the uncle designation is a very good one that can mean close biology or no biology at all. I suppose English could have went with “uncle in law” or “aunt in law” but it didn’t. But I do think that these familial titles are largely based on biology because the relationships themselves are–with the added provisions of adoption being a legal designation of biology, and the olde Christian idea that a married couple becomes one such that your biological aunt’s husband becomes your uncle.

70

The use of the terms “aunt” and “uncle” are good examples of where the words that are used don’t have to exactly match the technical definitions. Children (who speak English) often grow up referring to someone as “Aunt X” or “Uncle Y” even though they eventually learn that X and Y are technically the spouses of an uncle or an aunt, but that doesn’t stop them from continuing to call them by the not technically correct name. They may also grow up calling someone “Aunt X” or “Uncle Y” even though these people are the great-aunt or great-uncle.

71

I disagree with what you claim the definition of “aunt” or “uncle” are. I agree that your great uncle, or you mother’s best friend might be called uncle or aunt despite not meeting the technical definition. But i believe that the technical definition of aunt and uncle in English DO include the spouses of your parents’ siblings.

72

I disagree, though. She was my aunt previous to the marriage and remains so afterwards. I would never call her my step mother, because the term implies no biological connection and I have a closer relationship with her–aunt.

73

I believe she is simultaneously your aunt and your step mother. And either relationship might be more important to specify depending on the circumstances, (medical history? school pick up line?) but both are always true.

74

I know a guy who married a divorced woman. She had a young child from a previous marriage and said child lived with them. She was a nurse. She told the guy (her new husband), “If anything ever happens to me, I need you to let the doctors know that the man my son calls his father…isn’t, biologically.”

She had had an affair, got pregnant, didn’t tell the man she was married to—she just let him go on thinking he’d fathered the child. But as a nurse, she realized that if medical professionals assumed, in an emergency, that the child’s father would be a perfect match for a transplant or whatever…

Wasn’t there some “common knowledge” that went around that 25% of children weren’t fathered by the man they called dad? This article says most researchers think it’s actually less than 10.

If we’re debating genetics and relationships, precision of terminology is critical. I totally get that you may love a step brother like a biological brother, but for the purposes of this thread we need fully accurate descriptions.

BTW I recently learned that there is a third way to be a “brother-in-law.” I knew…

  1. My sibling’s husband is a brother-in-law
  2. My wife’s brother is a brother-in-law

What I didn’t know was…
3) My sister-in-law’s husband is my brother-in-law

That relationship seemed too remote—married to the sister of the woman I’m married to—but ok, ignorance fought.

75

In a text MUD I was playing a dwarven character where in that milieu, family was everything to that race. She went on a rant in Common to a human character once, “You Humans and your imprecision! Take ‘aunt’ for example. Is she your mother-sister or your mother-brother-wife or your father-sister or your father-brother-wife? And don’t even get me started on ‘cousin’!”

76

In some human languages, it would also matter whether it was your parent’s older sibling or their younger sibling. IIRC, Thai has different words for mother’s-younger-sibling, father’s-younger-sibling, parent’s-older-brother, or parent’s-older-sister. And yes, that does mean that in the first two cases, the sibling’s gender doesn’t matter, and in the latter two cases, the parent’s gender doesn’t matter.

77

How do they address these? Case-by-case basis?

It’s interesting how Spanish has two for cousin—primo, prima—depending on male or female. And in French, belle-soeur means -either- stepsister -or- sister-in-law. Each indicates a lack of blood relation but membership in the tribe, so to speak.

78

I was mistaken about that.

~Max

79

I think there’s a difference between how a person is addressed or referred to and how the relationship is described.

In my culture/dialect (whichever it actually is) , I address and refer to my cousin Joe as “Joe”. I would never address him as “Cousin Joe” and I would only refer to him as “Cousin Joe” if it was necessary to distinguish him from “Uncle Joe” or “Grandpa Joe” or something like that but if I’m describing the relationship to someone outside my family, he is my cousin. Similarly, if I am addressing or referring to one of my mother’s aunts or uncles, they are Aunt/Uncle Firstname but if you asked me how Laura is related to me, I would tell you she is my great aunt

80

Yeah, that makes sense. I still think that we don’t just “call your mother’s sister’s husband your uncle”, but that he IS your uncle as the words are defined in English.