What people call "Brussels" is
* The Brussels-Capital Region: https://www.openstreetmap.org/relation/54094
* An subdivision of Belgium called "arrondissement": https://www.openstreetmap.org/relation/2404020
* A city/municipality (technically, this one is the capital of Belgium): https://www.openstreetmap.org/relation/58274
* And much more

All those objects are properly mapped on OSM, each with proper references and correct wikidata and wikipedia links.

You may want to know that "CoMaps" only shows you a limited set of OSM data.  The confusion probably comes from there.  Since you did not provide any reference to an OSM object to tell exactly *what* was wrong and *what* you expected instead, we could only guess.