Tom is the boy .I went to the cinma with him together.把这两句合并为定语从句。

Tom is the boy .I went to the cinma with him together.把这两句合并为定语从句。

Tom is the boy with whom I went to the cinema together. 个人认为together放在后面比较好。
如果用who，应该把with放在后面，Tom is the boy who I went to the cinema together with.

I went to the cinema with Tom who is a boy together.

Tom is the boy together with whom i went to the cinema

I went to the cinma with Tom together who is the boy . 再看看别人怎么说的。