To mistakenly treat a villain or an enemy as one's own kin or trusted friend; to be utterly misguided in judgment regarding someone's true nature.
小明在生意场上缺乏经验，差点认贼作子，将合伙人的阴谋当成善意提醒。
Xiao Ming, lacking experience in business, almost mistook his partner's malicious scheme for a kind reminder, essentially taking a villain for his son.
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