嫂子 refers to the wife of one's older brother.
Topic 1.1: 1.1 Families and Communities in China
嫂子 (sǎo zi) cheat sheet for homework
弟媳 (dìxí): The wife of one's younger brother.
兄弟姐妹 (xiōngdì jiěmèi): Siblings; brothers and sisters.
夫妻 (fūqī): Husband and wife.