English doesn't have any way of distinguishing between my wife's sister, my brother's wife, and my wife's brother's wife. They are all sisters-in-law. But these 3 relationships are very different for many people in practice. My wife's sister grew up with someone I'm very close to and unlike most other relatives I can't usually badmouth her to my wife. My brother's wife is someone who, like my wife, entered as an adult into a family which I and my brother have always been part of and so might feel threatened by our closeness. And my wife's brother's wife is someone who I can bond with over "we both married into this crazy family and are not really like the rest of them".

And then from my kid's point of view, not only are these all 'auntie' but so is my very own sister.