通家之好 close family friendship
Explanation
指两家关系亲密，如同一家。形容两家世代友好，关系密切。
Refers to a close, familial relationship between two families that has lasted for generations.
Origin Story
王家和李家世代居住在同一个村庄，两家祖辈便有交往，后来两家孩子又成了儿女亲家，两家关系越来越密切，逢年过节，相互走动，互相帮助，俨然成了一个大家庭。村里人都说，王家和李家是真正的通家之好。
The Wang and Li families lived in the same village for generations. Their ancestors had known each other, and later, their children became in-laws, making their relationship even closer. During festivals, they visited each other, helped each other, and resembled a big family. Villagers said that the Wang and Li families were a true example of close friendship.
Usage
用于形容两家关系亲密，如同一家。
Used to describe the close, familial relationship between two families.
Examples
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两家世代交好，是通家之好。
liang jia shidai jiaohao, shi tongjia zhi hao
The two families have been friendly for generations; they are very close.
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他们两家是通家之好，经常走动。
tamen liang jia shi tongjia zhi hao, jingchang zou dong
Their families are close friends, often visiting each other.