The membership of the Involveds was necessarily fluid. It drew new members from maturing lesser civilizations. Very old and mature civilizations exited the Involveds when they withdrew from galactic affairs, becoming Elders or Sublimed.
The Involved were separated into at least three tiers: Low, Mid, and High Level. An Involved's tier roughly corresponded to its place on the Recognised Civilisationary Levels scale; Low Level corresponded to high Level 5 to low Level 6 civilizations, while High Level corresponded to Level 8 civilizations.