哥哥,其实我也很想你。只是不知道如何表达出来,我们都想彼此的。英语咋说？

Brother, I miss you too. I just don't know how to express it. We all miss each other.希望能帮到你！

Brother, acturally I miss you very much. I just don't know how to express it. In fact, we miss each other.

Big Brother, I miss you very much . But I don't know how to tell you. I think you are the same.
please adopt my answer, thanks.

如果哥哥也很想你，我觉得不知道怎么表达出来，你用英语也可以直接表达出来你们两个人想法。