Checking out some strong subreddit relationships stemming from a chosen root subreddit. The relationships below are ordered by User Overlap Scores from subredditstats.com. An interesting way of discovering related subreddits based on user overlap.
Interesting dichotomy of users between AgainstHateSubreddits and ConsumeProduct.
These glimpses use the User Overlap scores from https://subredditstats.com/subreddit-user-overlaps. Look up a subreddit yourself, for fun.