即使在子页面上，wp_list_pages也会显示子页面

i tried so many code snippets... but nothing worked. I need an menu what display sub and child pages like this:

On a page:
- Subpage 1 <-- You are here
- Subpage 2
-- Child 1
-- Child 2
-- Child 3
- Subpage 3

And

On a child page:
- Subpage 1 
- Subpage 2
-- Child 1
-- Child 2 <-- You are here
-- Child 3
- Subpage 3

The menu should only display the sub and child pages of the top parent page. Not all Wordpress subpages.

Edit: For exmaple I tried this, but on a child or subpage, it displays nothing

<?php
        global $post;
            wp_list_pages( array(
                'title_li'    => '',
                'child_of'    => $post->ID,
                'show_date'   => 'modified',
                'date_format' => $date_format
            ) );
        ?>