# What do you call this familial relationship? **URL:** \ **Category:** Factual Questions\ **Created:** [March 24, 2022, 8:28pm UTC](https://boards.straightdope.com/t/what-do-you-call-this-familial-relationship/961655 "2022-03-24T20:28:58Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![UltraVires](https://avatars.discourse-cdn.com/v4/letter/u/ecccb3/32.png) [@UltraVires](https://boards.straightdope.com/u/UltraVires)\ **Post date:** [March 24, 2022, 8:28pm UTC](https://boards.straightdope.com/t/what-do-you-call-this-familial-relationship/961655/1 "2022-03-24T20:28:58Z")
Let’s say a man marries a woman and they have a child Thomas. The woman dies and then the man marries the woman’s full blooded sister. Those two have a child Patrick. What name is given to the relationship between Thomas and Patrick? They are certainly half brothers, yet they also share two sets of common grandparents which is exactly like full blooded brothers. Three-quarter brothers? That also doesn’t seem right because their ancestral tree is identical throughout the ages (like full brothers) except for one single individual. Is there a name for this relationship? ---
**Author:** ![Max\_S](https://avatars.discourse-cdn.com/v4/letter/m/46a35a/32.png) [@Max\_S](https://boards.straightdope.com/u/Max_S)\ **Post date:** [March 24, 2022, 8:34pm UTC](https://boards.straightdope.com/t/what-do-you-call-this-familial-relationship/961655/2 "2022-03-24T20:34:45Z")
Step-brothers. ~Max ---
**Author:** ![UltraVires](https://avatars.discourse-cdn.com/v4/letter/u/ecccb3/32.png) [@UltraVires](https://boards.straightdope.com/u/UltraVires)\ **Post date:** [March 24, 2022, 8:35pm UTC](https://boards.straightdope.com/t/what-do-you-call-this-familial-relationship/961655/3 "2022-03-24T20:35:47Z")
Can’t be. They are biologically related through the father unless I stated it poorly. ---
**Author:** ![Seanette](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/seanette/32/9139_2.png) [@Seanette](https://boards.straightdope.com/u/Seanette)\ **Post date:** [March 24, 2022, 8:36pm UTC](https://boards.straightdope.com/t/what-do-you-call-this-familial-relationship/961655/4 "2022-03-24T20:36:25Z")
Not a single name that I know of. Via Dad, they’re half brothers (different mothers). The offspring of siblings are cousins, so along the maternal line(s), they’re first cousins. ---
**Author:** ![mbh](https://avatars.discourse-cdn.com/v4/letter/m/a6a055/32.png) [@mbh](https://boards.straightdope.com/u/mbh)\ **Post date:** [March 24, 2022, 8:38pm UTC](https://boards.straightdope.com/t/what-do-you-call-this-familial-relationship/961655/5 "2022-03-24T20:38:33Z")
Due to Levirate marriages, there might be a term for it in Hebrew, but I doubt if there is one in English. ---
**Author:** ![Max\_S](https://avatars.discourse-cdn.com/v4/letter/m/46a35a/32.png) [@Max\_S](https://boards.straightdope.com/u/Max_S)\ **Post date:** [March 24, 2022, 8:39pm UTC](https://boards.straightdope.com/t/what-do-you-call-this-familial-relationship/961655/6 "2022-03-24T20:39:02Z")
No, that only applies if the brother dies without children. ~Max ---
**Author:** ![Pardel-Lux](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pardel-lux/32/20182_2.png) [@Pardel-Lux](https://boards.straightdope.com/u/Pardel-Lux)\ **Post date:** [March 24, 2022, 8:39pm UTC](https://boards.straightdope.com/t/what-do-you-call-this-familial-relationship/961655/7 "2022-03-24T20:39:06Z")
That would be the square root of step-twins. ---
**Author:** ![UltraVires](https://avatars.discourse-cdn.com/v4/letter/u/ecccb3/32.png) [@UltraVires](https://boards.straightdope.com/u/UltraVires)\ **Post date:** [March 24, 2022, 8:44pm UTC](https://boards.straightdope.com/t/what-do-you-call-this-familial-relationship/961655/8 "2022-03-24T20:44:12Z")
> [@Seanette](#): > > The offspring of siblings are cousins, so along the maternal line(s), they’re first cousins. Wife and I had this argument today. 🙂 I say no. The offspring of siblings are cousins, but that assumes different father/mothers. The definition I have always heard is that cousins share a common set of grandparents. But it must mean ONLY one set or else all brothers would also be cousins. IOW: “First cousins” doesn’t do it justice; they are closer than that. They are also closer than half brothers. ---
**Author:** ![Max\_S](https://avatars.discourse-cdn.com/v4/letter/m/46a35a/32.png) [@Max\_S](https://boards.straightdope.com/u/Max_S)\ **Post date:** [March 24, 2022, 8:47pm UTC](https://boards.straightdope.com/t/what-do-you-call-this-familial-relationship/961655/9 "2022-03-24T20:47:18Z")
So if this is the family tree for Thomas - Thomas - Dad - Patrilineal Grandfather - Patrilineal Grandmother - Thomas’s Mom - Matrilineal Grandfather - Matrilineal Grandmother And this for Patrick - Patrick - Dad - Patrilineal Grandfather - Patrilineal Grandmother - Thomas’s Aunt (Patrick’s Mom) - Matrilineal Grandfather - Matrilineal Grandmother Thomas would be both Patrick’s half-brother and first cousin. I wonder if this was more prevalent in ye olden days, I imagine it would be common in cultures with polygamy. ~Max ---
**Author:** ![UltraVires](https://avatars.discourse-cdn.com/v4/letter/u/ecccb3/32.png) [@UltraVires](https://boards.straightdope.com/u/UltraVires)\ **Post date:** [March 24, 2022, 8:53pm UTC](https://boards.straightdope.com/t/what-do-you-call-this-familial-relationship/961655/10 "2022-03-24T20:53:27Z")
> [@Max\_S](#): > > So if this is the family tree for Thomas > > - Thomas > - Dad > - Patrilineal Grandfather > - Patrilineal Grandmother > > - Thomas’s Mom > - Matrilineal Grandfather > - Matrilineal Grandmother > > And this for Patrick > > - Patrick > - Dad > - Patrilineal Grandfather > - Patrilineal Grandmother > > - Thomas’s Aunt (Patrick’s Mom) > - Matrilineal Grandfather > - Matrilineal Grandmother Yes. One almost example is Stonewall Jackson. [Jackson Family Genealogy - VMI Archives - Virginia Military Institute](https://www.vmi.edu/archives/manuscripts/stonewall-jackson-resources/jackson-family-genealogy/) His first wife and the child died during childbirth. He married his now deceased wife’s sister and had children. Suppose his first wife had a child with him prior to the unfortunate early death. The relationship between that child and his other children would be what we are discussing. ---
**Author:** ![Max\_S](https://avatars.discourse-cdn.com/v4/letter/m/46a35a/32.png) [@Max\_S](https://boards.straightdope.com/u/Max_S)\ **Post date:** [March 24, 2022, 8:56pm UTC](https://boards.straightdope.com/t/what-do-you-call-this-familial-relationship/961655/11 "2022-03-24T20:56:18Z")
They would be step brothers, first cousins, and half brothers. All at the same time. Would probably just call themselves brothers. ~Max ---
**Author:** ![UltraVires](https://avatars.discourse-cdn.com/v4/letter/u/ecccb3/32.png) [@UltraVires](https://boards.straightdope.com/u/UltraVires)\ **Post date:** [March 24, 2022, 8:56pm UTC](https://boards.straightdope.com/t/what-do-you-call-this-familial-relationship/961655/12 "2022-03-24T20:56:23Z")
Also side note…rookie mistake…when posing this hypo to your wife, do not say “Now suppose I had kids with you sister…” Please rephrase. 🙂 ---
**Author:** ![UltraVires](https://avatars.discourse-cdn.com/v4/letter/u/ecccb3/32.png) [@UltraVires](https://boards.straightdope.com/u/UltraVires)\ **Post date:** [March 24, 2022, 8:57pm UTC](https://boards.straightdope.com/t/what-do-you-call-this-familial-relationship/961655/13 "2022-03-24T20:57:29Z")
They aren’t step brothers at all. I don’t see how that comes in. But if half brothers can also be cousins, then why not full brothers? ---
**Author:** ![Max\_S](https://avatars.discourse-cdn.com/v4/letter/m/46a35a/32.png) [@Max\_S](https://boards.straightdope.com/u/Max_S)\ **Post date:** [March 24, 2022, 8:59pm UTC](https://boards.straightdope.com/t/what-do-you-call-this-familial-relationship/961655/14 "2022-03-24T20:59:25Z")
When Dad re-marries, his wife becomes your step-mom. Patrick used to be a first cousin and half brother but is now also a step-brother. Unless the child was had after the marriage (now realizing that’s probably what you implied) it would be a step-brother. ~Max ---
**Author:** ![Max\_S](https://avatars.discourse-cdn.com/v4/letter/m/46a35a/32.png) [@Max\_S](https://boards.straightdope.com/u/Max_S)\ **Post date:** [March 24, 2022, 9:02pm UTC](https://boards.straightdope.com/t/what-do-you-call-this-familial-relationship/961655/15 "2022-03-24T21:02:47Z")
> [@UltraVires](#): > > But if half brothers can also be cousins, then why not full brothers? The genetics don’t work like that unless the sisters were identical twins. ~Max ---
**Author:** ![RitterSport](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rittersport/32/6326_2.png) [@RitterSport](https://boards.straightdope.com/u/RitterSport)\ **Post date:** [March 24, 2022, 9:03pm UTC](https://boards.straightdope.com/t/what-do-you-call-this-familial-relationship/961655/16 "2022-03-24T21:03:29Z")
All I can say is that, if they were opposite sex, they definitely shouldn’t reproduce. Anyway, half siblings, since they were never cousins before they were half siblings. Definitely not step siblings. I have a step mother and her son, my father’s son, is my half brother, not my step brother. ---
**Author:** ![UltraVires](https://avatars.discourse-cdn.com/v4/letter/u/ecccb3/32.png) [@UltraVires](https://boards.straightdope.com/u/UltraVires)\ **Post date:** [March 24, 2022, 9:04pm UTC](https://boards.straightdope.com/t/what-do-you-call-this-familial-relationship/961655/17 "2022-03-24T21:04:25Z")
> [@Max\_S](#): > > The genetics don’t work like that unless the sisters were identical twins. > > ~Max Even if the sisters were identical twins, nobody would call them both brothers and cousins. Isn’t this sort of an “a greater subsumes the lesser” status? They are not cousins because they have a closer relationship: that of half-brothers. Yet, their relationship is even closer than that. ETA: As I think more, half-brothers and cousins are pretty much genetically the same. They share one common set of grandparents and the other set are strangers one to the other. This is more than that as they have two common sets of grandparents, but are not full brothers. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [March 24, 2022, 9:08pm UTC](https://boards.straightdope.com/t/what-do-you-call-this-familial-relationship/961655/18 "2022-03-24T21:08:30Z")
> [@UltraVires](#): > > But it must mean ONLY one set or else all brothers would also be cousins. All brothers are, in fact, cousins. Zeroth cousins, if you want to be more precise about it. And there’s also such a thing as double cousins, where a pair of siblings from one family marry respectively a pair of siblings from another family, and then have kids. Those kids definitely aren’t siblings, but still have all four grandparents in common. ---
**Author:** ![UltraVires](https://avatars.discourse-cdn.com/v4/letter/u/ecccb3/32.png) [@UltraVires](https://boards.straightdope.com/u/UltraVires)\ **Post date:** [March 24, 2022, 9:09pm UTC](https://boards.straightdope.com/t/what-do-you-call-this-familial-relationship/961655/19 "2022-03-24T21:09:48Z")
> [@Chronos](#): > > And there’s also such a thing as double cousins, where a pair of siblings from one family marry respectively a pair of siblings from another family, and then have kids. Those kids definitely aren’t siblings, but still have all four grandparents in common. Yes. Interesting. Yet, this relationship is closer than that. Double cousins share both grandparents but have two different parents. ---
**Author:** ![RitterSport](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rittersport/32/6326_2.png) [@RitterSport](https://boards.straightdope.com/u/RitterSport)\ **Post date:** [March 24, 2022, 9:10pm UTC](https://boards.straightdope.com/t/what-do-you-call-this-familial-relationship/961655/20 "2022-03-24T21:10:43Z")
Unless the father and sister immediately become estranged, they will grow up just like brothers, not like cousins, so I would say (again) that they are half-brothers. [Next page](https://boards.straightdope.com/t/what-do-you-call-this-familial-relationship/961655.md?page=2)