Is there a name for this relationship?

[Wabi Sabi]

If two sisters both have children by the same man, the resulting offspring are both half siblings and full first cousins. Is there a name for this relationship?

[Tanaqui]

Double first cousins are two children who are cousins where both sets of parents are siblings - like if a girl and her brother married a boy and his sister.

So I'd say that if they're not raised together and don't feel very close, they could call themselves double first cousins. That's the closest term.

But if they are raised together or if they do feel close to each other then they should probably just say they're siblings.

[alisoncooks]

Well, I know a woman who has children by two men (brothers) - those children are cousins and half sibs, but they refer to each other as siblings. (Perhaps a bit different, though...first husband died, later she marries his brother and has kids.)

[Lawyer&Mom]

My great-grandmother was an identical twin.  My grandmother and her siblings were especially close to their cousins.  Genetically they were half siblings.  (And they lived next door.)

[bolt.]

I think the half-sibling relationship would be used as the primary definition, since it defines the closest degree of relation. There isn’t a term (that I know of) that contains both forms of relationship between them. They would be “Half siblings who are also (first) cousins.”

In other cases where people are related in two distinct ways they are defined by their closest degree of relation. (Ie. Two people who are biological cousins and marry into the same family would be both ‘in laws’ and cousins, but the cousin relationship is primary.)

[gardenmom5]

they are halfsiblings.

after her sister died, my widowed 2nd great-grandmother married her sister's husband.  practical standpoint of her sister's children were younger, and she already had an emotional attachment to them.  they had two children together (I descend from this marriage).    I've done genealogy for more than 30 years - and they've always been referred to as half-siblings to each of their parents three older children.  (re: six older children in total)

 

eta: the older children would be step-siblings (reared in the same house), and full cousins.

[gardenmom5]

2 hours ago, Tanaqui said:

Double first cousins are two children who are cousins where both sets of parents are siblings - like if a girl and her brother married a boy and his sister.

So I'd say that if they're not raised together and don't feel very close, they could call themselves double first cousins. That's the closest term.

But if they are raised together or if they do feel close to each other then they should probably just say they're siblings.

double first cousins still have separate parents, and it is not the same as sharing a parent.  which is what I believe the question was about.

My mother had double first cousins. 

[SKL]

I would refer to them as half siblings.  Unless you are looking for some scientific terminology - then I don't know.

[Tanaqui]

True, but as I said that's the closest term. I don't think there's an exact term in English for this exact situation. If they consider themselves cousins then they're double first cousins. If they consider themselves siblings then they're siblings.

[TechWife]

My husband’s cousins became his step-siblings, bit they were all adults when this occurred (my father-in-law married his first wife’s sister-in-law, both my husband’s mother and her brother had died). They still refer to each other as cousins unless they are joking around, the it’s “cousin-step-brother” and “cousin-step-sister.” 

[Ottakee]

In our family, it is referred to as siblings.  Then again we also have "your brother's brother's brother" and a dad with 2 sons----all with the same first name.

[Ravin]

Three quarter siblings, if you want to get creative.

[Bluegoat]

I'd say half siblings.  I guess if I was trying to be technical I'd just have to explain it.

There have been cultures IIRC where it was normal, if a man died, for his wife remarried his brother, and her kids with the second brother were sometimes considered to be the kids of the first brother.

[scoutingmom]

Half siblings, who are also cousins.

Step-siblings are related only through marriage of the parents.

[foxbridgeacademy]

I had a friend who had children with her sister's ex.... the kids considered themselves just siblings/half siblings and the whole cousin issue was avoided.

[Bluegoat]

I watched a show years ago where a woman had a kid with her SO, and then later with the SO's grown son.  I thought that was an awkward one.

[Scarlett]

8 minutes ago, Bluegoat said:

I watched a show years ago where a woman had a kid with her SO, and then later with the SO's grown son.  I thought that was an awkward one.

Yes.  Icky.

[katilac]

17 hours ago, Tanaqui said:

True, but as I said that's the closest term. I don't think there's an exact term in English for this exact situation. If they consider themselves cousins then they're double first cousins. If they consider themselves siblings then they're siblings.

 

I would find it pretty strange if someone used the term cousin and then I found out they were siblings. It has nothing to do with how close you are or if you were raised together. People can use whatever term they prefer, but it would just cause more talk imo.