I'm planning a game where there is about a dozen important NPC actors, with some more less important ones. "Important" means that even if they are not directly involved in current events, they play a large role in the world which cannot be discounted and their existence is obvious to anyone in-character.
However, I know that humans count 1-2-3-many and can only focus on 6-7 things on average at the same time. If I introduce a lot of NPCs, at some point my players will be confused who's who and who was that guy again?
I'm looking for technique or paradigm that allows me to marry the ideas of approachable player space and multiple important NPCs.