I tried using the two sample codes from the documentation page but it still shows the related videos (also tested it on a page instead of a sidebar text widget)
[video_lightbox_youtube video_id=”G7z74BvLWUg&rel=0″ width=”640″ height=”480″ anchor=”click me”]
[video_lightbox_youtube video_id=”G7z74BvLWUg&rel=false” width=”640″ height=”480″ anchor=”click me”]