Or, embed this snippet using GenerateWP WordPress Plugin.

Download

Clone

if elseif parent

Generate code based on the parent page

<?php
			if ( $post->post_parent == parentID {
			echo 'CONTENT HERE';
			} elseif ( $post->post_parent == parentID ) {
			echo 'CONTENT HERE';
			} elseif ( $post->post_parent == parentID ) {
			echo 'CONTENT HERE';
			}
?>