loop hierarchical custom post type, child pages only

<?php
// query only child pages of custom post type
$customQuery = array(
    'post_type' => 'CUSTOM_POST_TYPE',
    'posts_per_page' => '10',
    'post_parent__not_in' => array(0),
    );
$custom = new WP_Query( $customQuery );
if ($custom->have_posts()) :
while ( $custom->have_posts()) : $custom->the_post();
?>

DO STUFF
            
<?php endwhile;
endif;
wp_reset_query(); ?>