global $post;

$parentID = $post->post_parent; //Shows 2068
$currID = $post->ID; //Shows 2069

$args = array('post_parent' => $post->ID, 'post_type' => 'projects', 'numberposts' => -1  );
        $children = get_children($args);

        foreach ($children as $child):
            $childIDs .= " ".$child->ID; //Get Children IDs
        endforeach;

$allIDs = $parentID." ".$currID.$childIDs; //shows 2068 2069 2070 2071

add_filter( 'ajax_query_attachments_args', 'wpb_show_current_user_attachments');

function wpb_show_current_user_attachments( $query, $allIDs ) {

    $allIDarray = explode (" ", $allIDs);
    //$user_id = get_current_user_id();

    if ( $user_id && !current_user_can('activate_plugins') && !current_user_can('edit_others_posts') ) {

        // $query['author'] = $user_id;
        $query['post_parent'] = $allIDarray;

    }
    return $query;
}

function restrict_media_images_per_post_type($query) {
    add_filter('posts_where', 'media_posts_where');
    add_filter('posts_join', 'media_posts_join');
    return $query;
}
add_filter('ajax_query_attachments_args', 'restrict_media_images_per_post_type');

function media_posts_where($where) {
    global $wpdb;
    $post_id = false;
    $whitelist_post_type = array(
        'post',
        '{custom post type}' //change this according to your need e.g. projects
    );
    if ( isset($_POST['post_id']) ) {
        $post_id = $_POST['post_id'];
        $post = get_post($post_id);
        if ( $post && in_array($post->post_type, $whitelist_post_type)) {
            $where .= $wpdb->prepare(" AND my_post_parent.post_type = %s ", $post->post_type);
            //$where .= $wpdb->prepare(" AND my_post_parent.post_type = %s AND {$wpdb->posts}.post_parent = %d", $post->post_type, $_POST['post_id']);  //Use this if you want to restrict to selected post only
        }
    }
    return $where;
}

function media_posts_join($join) {
    global $wpdb;
    if ( isset($_POST['post_id']) ) {
        $join .= " LEFT JOIN {$wpdb->posts} as my_post_parent ON ({$wpdb->posts}.post_parent = my_post_parent.ID) ";
    }
    return $join;
}