Joshua 21:40

As for the cities of the several Merarite clans , that is, the remainder of the clans of the Levites , those allotted to them were in all twelve cities .

The total number of towns allotted to the Merarite clans, who were the rest of the Levites, came to twelve.

So all the cities for the children of Merari by their families, which were remaining of the families of the Levites, were by their lot twelve cities.