The only (easy) way this can be done is to query all special
, calculate their depth, and then build a new stack of 3-level deep:
$grandkids = array();
$specials = get_posts(
array(
'posts_per_page' => -1,
'order' => 'DESC',
)
);
foreach ( $specials as $special ) {
if ( count( get_post_ancestors( $special ) ) === 2 ) {
$grandkids[] = $special;
if ( count( $grandkids ) === 3 )
break;
}
}
foreach ( $grandkids as $post ) {
setup_postdata( $post );
// Do your stuff
}