In-laws once removed
The other day I started wondering there are terms to describe your relationship with your in-law’s relatives. For example, my sister’s husband is my brother-in-law, but is his sister some kind of in-law to me? She is my sister’s sister-in-law, but as far I can work out, there is no particular term to describe my remote connection to her – sister-in-law once removed, perhaps. Then there’s her husband and their children – are they any kind of in-laws to my sister or me?
Are specific terms for relationships in any of the languages you know?
According to the Online Etymology Dictionary, in-law is “anyone of a relationship not natural” and the earliest known use of the phrase in writing was in the form of brother-in-law. The law in question is Canon Law (church law), which defines degrees of relationship within which marriage is prohibited.