This isn't an attempt to be funny, this is really how I think about the Eeveelutions
I used to group Espeon, Umbreon, and Sylveon into "friendship Eeveelutions", but that's wrong, since apparently Sylveon evolves with affection and not with friendship.
So Sylveon is just on its own
Espeon and Umbreon really are counterparts of each other, though...