Korean Family Titles
처남
cheonam · Wife's brother
Relationship
my wife → her brother
Who uses it
A husband, about his wife's brother.
When you call them
If he's older than your wife, call him 형님 (hyeongnim); if younger, 처남.
When you talk about them
To others, 처남 either way.
Example
처남, 이번에 이사 도와줘서 고마워.Cheonam, thanks for helping with the move.
Based on the standard etiquette of the National Institute of Korean Language; families and regions vary.