家丑不可外扬 (jiā chǒu bù kě wài yáng)

家丑不可外扬

(jiā chǒu bù kě wài yáng)
English Translation: “Family shames must not be publicized.”

Meaning:
Problems that happen within the family should be resolved within the family and not made public.

Example:
他们的家庭问题应该自己解决，家丑不可外扬。
(Their family problems should be resolved privately—“family shames must not be publicized.”)

Source: Hello Mandarin