List parents and child pages of curent child page

Ok after I spent whole morning trying and testing various stuff I came here to cry for help. This is my situation

Level 1
  -level 2
  -level 2
  -level 2
     -level 3
     -level 3
     -level 3
  -level 2
Level 1
Level 1

Ok I want when I`m on level 3 pages to list all level 3 and level 2 pages from same level 1 parent.

I tried with this but no luck:

<?php
                    $output = wp_list_pages('echo=0&depth=1&title_li=');
                    if (is_page()) {
                        $page = $post->ID;
                        if ($post->post_parent) {
                            $page = $post->post_parent;
                        }
                        $children = wp_list_pages('echo=0&child_of=' . $page . '&title_li=');
                        if ($children) {
                            $output = wp_list_pages('echo=0&child_of=' . $page . '&title_li=');
                        }
                    }
                    echo $output;
                    ?>