Their relationship is only one between the superior and the inferior,and nothing else special.

and前是不是省略了there is?

【答】不是省略了there is。这种省略一般是承前省略重复的部分，即：省略了主语和系动词。

Their relationship is only one between the superior and the inferior, and nothing else special.（简练）

等于：

Their relationship is only one between the superior and the inferior, and their relationship is nothing else special.（啰嗦）

等于：

Their relationship is only one between the superior and the inferior, and it is nothing else special.（较好）

【翻译】他们的关系只是一种上级和下级之间的关系，不是什么其他特别的（关系）。