What do you call for brother's wife?

Answer 1

Your brother's wife is your sister-in-law. It is appropriate to call her by her first name, however, if you want to use a diminutive of her name (ie calling Elizabeth Beckie), please check with her first. Some people are not comfortable, nor do they like "nicknames".

In the English language, no distinction is made between the wife of a younger brother and the wife of an older brother. The wife of your brother is simply your sister-in-law.