兄と間違えた

mistook … for my older brother

→ 兄
phrase Rare #30,173
mistook … for my older brother 兄 means the speaker’s older brother; と marks the person they were mistaken for.
JA: あの人を兄と間違えた。
EN: I mistook that person for my older brother.

彼女は私を兄と間違えた。

She mistook me for my older brother.

君を兄と間違えた。

I mistook you for my older brother.

あなたを兄と間違えた。

I mistook you for my older brother.

彼は私の事を双子の兄と間違えた。

He mistook me for my twin brother.