Brother-in-law, a dialect, is a kind of address between relatives, referring to the husband's younger brother. Because all his children call him uncle, after a long time, this title naturally evolved. Many places in the north call their husbands' brothers and sisters-in-law; A husband's brother is called an uncle.

Brother-in-law and sister-in-law correspond to each other, which is called uncle-sister relationship. In the northeast folk, the expression of the relationship between uncle and sister-in-law can be casual and joking, which makes it more cordial and harmonious.

There is an unusual meaning in the relationship between uncle and sister-in-law, which comes from the drama Bao Gong Atonement. There is a folk saying that "an old sister-in-law is better than her mother", which means that her sister-in-law has a kind of affection that transcends generations, and the story of her sister-in-law raising her sister-in-law is often passed down as a much-told story.

The relationship with her brother-in-law is called Daboko, who is her husband's brother. The corresponding relationship is the brother's daughter-in-law. In northeast folk customs, the relationship between uncle and nephew is very serious. The two sides must never make fun of each other, or they will be laughed at.