List subpages of parent page (with parent page title) in Wordpress

list-subpages.php

<?php if ( is_page() ) { ?>

<?php
if($post->post_parent)
$children = wp_list_pages('title_li=&child_of='.$post->post_parent.'&echo=0'); else
$children = wp_list_pages('title_li=&child_of='.$post->ID.'&echo=0');
if ($children) { ?>

<h4>
<?php
$parent_link = get_permalink($post->post_parent);
$parent_title = get_the_title($post->post_parent);
?>
<a href="<?php echo $parent_link; ?>" ><?php echo $parent_title; ?></a>

</h4>

<ul class="subpages">
<?php echo $children; ?>
</ul>

<?php } } ?>