YOU SAID:
He ain't your friend brother.
INTO JAPANESE
彼はあなたの友達の兄弟ではありません。
BACK INTO ENGLISH
He is not your friend's brother.
INTO JAPANESE
彼はあなたの友達の兄弟ではありません。
BACK INTO ENGLISH
He is not your friend's brother.
That didn't even make that much sense in English.