The term Illyria is a name for the group of lands inhabited by different Illyrian tribes.
The Illyrians were Indo-European tribes in the Balkan Peninsula, who appeared around 1000 B.C. The Illyrians were divided into tribes. Each tribe was a self-governing community with a council of elders and a chosen leader. One leader, if strong enough, could unite several tribes into a kingdom.
There is no record of one king ruling over all of Illyria.
Thus, when one is talking about a “kingdom of Illyria” they are talking about a group of different tribes united by a leader at a specific point in time. Therefore the political entity called “kingdom of Illyria” varied in time and space.