From what I've known from watching Chinese dramas, siblings or fellow disciples may refer to each other as "big brother/sister" (oldest/first), "2nd/3rd brother/sister" (in-between), or "little brother/sister" (youngest/last). But I came across a translation of Hometown (故鄉) by Lu Xun, in which there's a lady known only as 杨二嫂 (I Googled this Chinese form) which I'm guessing means "wife of a guy who is the second sibling". Could anyone there who's read this one tell me what it really means? If that woman is called "Second Older Aunt-in-Law Yang", would it make her husband "Second Older Uncle Yang"? (by the way, is "Yang" her name or her husband's name?) Does this work the same way for women and their husbands? And does it work the same way with "younger uncles/aunts"?
嫂 means 'sister-in-law'
杨二嫂 means 'wife of Yang's family's second son'. It doesn't matter if you are the elder son or third son in the Yang family, she is still 二嫂 (second sister in law) to you (二 here doesn't indicate older or younger, it indicates second born)
Outsiders would call her 杨二嫂 to indicate they are addressing the 'Yang' family's second daughter-in-law.
"Second aunt-in-Law Yang" is 杨二嬸
"Second uncle-in-Law Yang" is 杨二叔