Check if page is grandchild

amIgrandchild.php

https://wordpress.org/support/topic/conditional-statement-is-page-a-grandchild?replies=6
http://wordpress.stackexchange.com/questions/182017/a-check-for-if-is-parent-page-if-has-children-if-has-grandchildren

<?php if( count(get_post_ancestors($post->ID)) == 2 ) echo 'this is grandchild of top page';  ?>
<?php if( count(get_post_ancestors($post->ID)) >= 2 ) echo 'this is grandchild of some page';  ?>

try and echo the post id before the code to see if it is the one of the page you are on:
maybe also add a is_page() conditional:

<?php
echo $post->ID; // should be the id of the current page
if( is_page() && count(get_post_ancestors($post->ID)) == 2 ) echo 'this is grandchild of top page';  ?>
where in your site are you using this code?