The Seven Peoples

These are the folk who largely populate the Combine:

The Balla
Cybes
The Durugh
Humans
Kch-Thk
The Tavak
The Vas Mal

Other Sentients

These races also belong to the Combine, but aren’t as widespread as the Seven Peoples.
The Cloddhucks
Haydrossi
Icti
Ndoaites
Raconid
Verpid

Non-Combine Sentients

The Missec
Ur

Class-K Entities

Dangerous beings which Combine law requires Lasers and other capable sentients to exterminate on sight.
Crysolis