Related videos are disabled in the embed created by AllVideos for some time now, but...
Google recently released a new update to the way some of their embed code parameters work, and unfortunately, that means when you try to share it, the option to disable or remove these related videos has completely gone. Google believes that related videos are an essential part of their UI (user interface) and are now promoting the feature.
Even though you can no longer prevent or hide the related videos from appearing at the end of the video, you can still use it to your advantage! Now, if your URL parameter is still set as “rel=0”, it will show related videos from YOUR channel, instead of showing competitors. In one way this can promote your audience to continue watching more videos by you and the only requirement is that you have more than 1 video on your channel.
As of this update being posted, there is no way to hide this on YouTube anymore. If the new way of displaying these videos isn’t what you’re looking for, there are other options than just using YouTube to host your videos, some of them involve additional cost and can have some restrictions involved.
The above is taken from the updated version of this article:
www.geekytech.co.uk/remove-disable-related-videos-youtube-embed/
Official announcement from YouTube:
developers.google.com/youtube/player_parameters#release_notes_08_23_2018