Are you talking about the suggested channels on the profile page?They talk about suggestions of people to follow on the right side of the screen,
You nailed it on this response.Are you talking about the suggested channels on the profile page?
Anyway, I don't think just subscribing will help much. However, ENGAGING in the community of a big Youtuber will! Get involved in their comments, events and social media and people will start recognizing your name at some point. I'm not saying you should spam comments all over their videos, but I'm talking about activily contributing to their community.
I was once a related channel to PewDiePie. I don't think its about size, however, similar content and tags perhaps.Related channels are not related to who you are subscribed to, it's related to if you make similar content and general size, subscribe to people you like don't do it just because you want promotion.