You know how you can't raze a city state ... but ...
I started a huge earth map game recently, and 3 city states spawned near me.
Or rather, it was turn 1, and those 3 city states are 3 settlers.
My warrior captured 1 of them in turn 1.
On their turn, one of them built a city, but the other was too close, so it moved closer to my warrior.
Captured turn 2.
So ... that start was like ... having 2 less city states and I had 2 extra workers.
I thought about it abit, and then started a new game.
Now, usually city states don't spawn that close, so it could have been due to the terrain and resource distribution on an earth map.
If that's the case, then maybe other civs can spawn that close, too ... and I wonder what would happen if you capture their settler with your warrior ...