remove_others_children_2.php

<?php
add_filter('wp_list_pages_excludes', 'remove_others_children');
function remove_others_children($excludes = array()) {
	$all_pages = get_pages();
	$all_children = (array) get_page_children(true, $all_pages);
	foreach ( $all_children as $child )
		$excludes[] = $child->ID;

	if ( ! is_page() )
		return $excludes;

	global $post;

	$this_heirarchy = (array) $post->ancestors;
	$this_children = (array) get_page_children($post->ID, $all_pages);
	foreach ( $this_heirarchy as $ancestor )
		$this_children = array_merge($this_children, (array) get_page_children($ancestor, $all_pages));

	foreach ($this_children as $child)
		$this_heirarchy[] = $child->ID;

	return array_diff($excludes, $this_heirarchy);
}
?>