you have a brother, who is married to a girl named gwen. gwen has a sister whose name is Ivy. what is your relationship with gwen's sister a. k.a Ivy ( like the term in the family, is she called sister in law or there another name for that)?

There is no specific term for my sister-in-law's sister. She and I have no relation or connection except through the marriage of our siblings.

Explanation:

Though there are terms and ways by which one can refer to people who are related not through blood. For instance, the wife of one's brother is called the sister-in-law and so on.

But for the specific case of the sister of one's sister-in-law, there is no specific term for it. This is because, logically, even though she is your sister-in-law, that is where the relationship between you and her family ends. Even though her family may be the "in-laws" of your brother, that doesn't necessarily make it yours.

So, my sister-in-law Gwen's sister Ivy will be just "Ivy" to me and cannot be referred to any particular term.