my mother is ateacher.my father is ateacher,too合并成一句My mother is a teacher,＿ ＿ my father.

Both my mother and my father are teachers.
Both my parents are teachers.

不对，不可以这样用的，正确的说法应该是My mother is a teacher, the same with my father。

Both my mother and my father are teachers.

多个 and

my parents are teacher

My mother is a teacher, so is my father.
倒装结构 so +动词+主语（肯定） neither（或nor） +动词+主语（否定） 用于表示也。。

My mother and father are both teachers

Both of my parents are teachers.

My mother is a teacher,＿ ＿ my father.so is
My mother is a teacher,so is my father.
我妈妈是老师,我爸爸也一样是老师.

Both my parents are teachers.

Both my mother and my father are ateachers.