If you count EVERY known member, real or cartoon, there is 14+. 2-Jamie and Damon, 5-Noodle, Cyborg, 2D, Murdoc and Russel, 7-the live band/recorders and the others are collaborators.
Well there are 4 characters in the "band" (5 if you count th cyborg), but Damon Albarn is the only permanent member of the real band. Gorillaz was founded by both Damon and Jamie Hewlett, so that's where the 2 comes in.