As established in The Lion King II: Simba's Pride, there was a whole sect of the pride who still supported Scar, led by the lioness Zira. These supporters were banished from the Pride Lands by ...

There she meets a lion cub named ... that Kovu is the son of Zira - a banished follower of the now-dead Scar. She plans to raise Kovu to overthrow Simba and become the king of the Pride Lands.

In the original film, Simba was tricked into thinking he killed his father, a guilt ridden lion cub flees into exile and abandons his identity as the future King.