he is the person to whom you ought to a

he is the person to whom you ought to a

he is the person是主句，to whom you ought to address the request是定语从句。to实际上是address the request to sb.中的介词，定语从句中引导词为which或whom时可以将to从固定搭配中移动到引导词前，以示句子没有缺成分（误导）。
追答：to whom中whom就相当于固定搭配中的sb.，但由于whom起引导定语从句的作用，是不能随便移动的，因此将to前移