子こで子こにならぬほととぎす

expression

a foster child never truly becomes one's own

Proverb meaning that no matter how lovingly you raise a foster child, they are not your biological child. Rare and literary.

• 「子こで子こにならぬほととぎす」ということわざがある。

  There is a proverb: 'A foster child never truly becomes one's own.'