Show list of Child Post in Parent Post

This would do it..

function get_child_pages() {
    global $post;
    $query = new WP_Query( array( 'post_parent' => $post->ID ) );

    if ( $query->have_posts() ) {
        echo '<ul>';
    while ( $query->have_posts() ) {
        $query->the_post();
            //Child pages
            echo '<li>' . get_the_title() . '</li>';
    }
        echo '</ul>';
    } else {
     echo 'Sorry, No posts found.';
    wp_reset_postdata();
}