I believe it was stated by one of the devs that it is in fact possible for city states to conquer and hence capture other cities. However it will probably be uncommon and they can't actively build new cities.
I'm unsure if they've changed this rule more recently, and I think it's highly unlikely that a city state will reach 10 cities even if it technically can, but I say give the OP a break. Not everyone here follows the details of all the game mechanics semi-religiously.
I'm unsure if they've changed this rule more recently, and I think it's highly unlikely that a city state will reach 10 cities even if it technically can, but I say give the OP a break. Not everyone here follows the details of all the game mechanics semi-religiously.