若指某人熟悉某事物，familiar 后连用介词 with。如：

Are you familiar with these details? 你熟悉这些细节吗？

若指某事物为某人所熟悉，familiar 后连用介词 to。如：

His voice on the phone sounded familiar to me. 他在电话上的声音我听起来很熟悉。

比较下面两句：

We are familiar with his name. 我们熟悉他的名字。

His name is familiar to us. 他的名字我们熟悉。