His father and my teacherteaches French.
請問這個句子的 teaches 用得對嗎？為何不需要 teach 呢？
His father and my teacher teaches French.
一般不會如此說。你的句子要想理解為理解的句子，只有一種可能，就是將 His father and my teacher 理解為“并列同位”結構，即屬并列結構，但表同位關系，即 His fatherand my teacher 指同一個人，句意：他的爸爸也就是我的老師是教法語的。
假如要理解為兩個人，需要用復數動詞 teach。