Her parents are all\all are\are both\both are English teachers.

Her parents are all\all are\are both\both are English teachers.

首先不能用all,因为all的适用范围是3者及以上,parents很显然是2者,所以一定要使用both
这个句子中用are both
即：Her parents are both English teachers.
也可以both提前置于句首：
Both of her parents are English teachers.

are both
both 指的是两者
all指三者或以上
然后are是be动词 一般前置 例如
they are all students. (三者以上)
如果是动词 就要后置 例如
you and i both like M.J