MySQL Query To Select Post By Postmeta

If I understand the question you are trying to show both post on single.php something like this should work as a second loop.

Put This INSIDE the first loop. Do this so you can get the current post ID

$parent_id=the_ID();

// Second Loop
$query = new WP_Query( array ( 'post_type' => 'TYPE1', 'meta_key' => $parent_id ) );

while ( $query->have_posts() ) : $query->the_post();
//normal loop stuff such as the_content();
    echo '<li>';
    the_title();
    echo '</li>';
endwhile;