Until now new civs only seemed to come from new one planet civs.
I'ld love to see additional ways in which civs are born, forged, created, ...

• Pirate nations (that you can pay to harass other civs)
• Planets with revolutions, after being unhappy for to long and not being under the influence of another civ
• Waring civs that unite (and form one new civ) against a common foe (as an alternative to surrendering)
• Coalitions, for example of one planet civs that unite for practical reasons (allowing members to leave)
• Lost civs that where displaced, out of phase, invisible, formerly non corporeal, or anything similar
• Asteroids and planets that are adrift and allow life (over time)
• Precursor planet forming modules (for instance by using nearby planetoid materials like asteroids, rings, ...)
• ...