Look what I found [see the screenshot]. I used this service -> Stats.video. Just insert "YouTube Channel's Name or ID" in the field and you'll get a list of all existing YouTube channels with this name.
I think the real channel is the one that has the most subscribers. But this is not the only advantage of this service: Here you can see the full statistics of the channel, you can find the most popular channels in any category, in any country and much more.