So, my aunt and uncle divorced a while back. My cousin, let's name her "Ariel", was my aunt's kid, and my uncle was her stepdad. I'm related to my uncle; my "Aunt" was his wife. And as I said, my aunt left him (which I guess technically means she's not my aunt anymore). So what does that make Ariel?
- The son or daughter of someone's step-uncle or step-aunt.
- The stepson or stepdaughter of someone's uncle or aunt.
- The stepson or stepdaughter of someone's step-uncle or step-aunt.
We normally refer to an uncle’s wife as an aunt but that doesn’t make it so, any more than calling a long-standing family friend with no actual relationship Aunt or Uncle makes it so.
I think my uncle’s wife is my aunt by marriage, not even my aunt-in-law (I’ve never heard such a term); certainly not really my aunt. I don’t think that’s different anywhere.
Unless the uncle adopted the girl, I think her only relationship to anyone but her mother would be step, as in step-cousin. In that case I suspect if the aunt “merely” left him it would make no difference to anything but if they were divorced, the step-relationship would cease along with the marriage.
As an uncle’s natural daughter would be your natural cousin, his step-daughter should be your step-cousin but the law might say that’s merely a social convention and no legal relationship exits (as at https://www.reference.com/family/step-cousin-f79762f39431ac31)
If the uncle legally adopted the girl, I suspect that would make her your adoptive and very possibly in law your natural cousin as well, and I wouldn’t be surprised if in some jurisdictions, it made her a natural and an adoptive and a step-cousin. complicated but it could work along the lines of European royal families where it might matter a great deal, or among Mark Twain’s river-folk, who sometimes have different degrees of relationship on their fathers’ and mothers’ sides. Let’s leave out the perverse relationships that incest can create.
The people who’d really know would be probate lawyers or European heralds.
In no case does “ex-“ necessarily imply ill will. Otherwise, ohwilleke is right about the flexibility of “cousin”:
You happen to bump into someone you know; you introduce her as your cousin, pure and simple.
You go together to supper with friends; you introduce her as your cousin and almost certainly, someone asks: “On which side?” in which case the whole evening might be spend just as above…