YouTube video on Redactor (final frame)

Hi, A client has pointed out that using YouTube embedded code on Redactor in Perch, displays video okay fine but has the annoying related videos end frame. Normally when you amend the embed a YouTube embed string to include ?rel=0 at the end, it prevents the YouTube from doing this. as per below link :

https://www.illuminea.com/remove-related-videos-from-end-of-embedded-youtube-video/

However Redactor ignore this. Has this ever been flagged before and is there a fix/workaround for it? My site in question has a purpose built video block that takes the source code and when you add this ?rel=0 string to end, it prevents the related video final frame from appearing. Any ideas?

Summary information
Perch: 3.1.1, PHP: 5.6.35, MySQL: mysqlnd 5.0.11-dev - 20120503 - $Id: 76b08b24596e12d4553bd41fc93cccd5bac2fe7a $, with PDO
Server OS: Linux, litespeed
Installed apps: content (3.1.1), assets (3.1.1), categories (3.1.1), perch_blog (5.6.1)
App runtimes: <?php $apps_list = array( 'content', 'perch_blog', );
PERCH_LOGINPATH: /perch
PERCH_PATH: /home/mcevoycraig/public_html/perch
PERCH_CORE: /home/mcevoycraig/public_html/perch/core
PERCH_RESFILEPATH: /home/mcevoycraig/public_html/perch/resources
Image manipulation: GD
PHP limits: Max upload 100M, Max POST 64M, Memory: 128M, Total max file upload: 64M
F1: 3b606135b33e6a102526838f4152a807
Resource folder writeable: Yes
HTTP_HOST: www.mcevoycraig.ie
DOCUMENT_ROOT: /home/mcevoycraig/public_html
REQUEST_URI: /perch/core/settings/diagnostics/
SCRIPT_NAME: /perch/core/settings/diagnostics/index.php