In The Lion King II: Simba's Pride the Outsiders were banished for supporting Scar, but in the original film, all of the lionesses supported Sarabi and also Simba, after he returned. So where did those outsiders come from?
According to the Lion King Fan Wiki, The Outsiders were an offshoot of Simba's pride, who decided to remain loyal to Scar after his death. We are suppose to assume that they were there during the course of the first film and that not all of the lionesses supported Simba after all.
Outsiders (also known as Outlanders) are an offshoot of Simba's pride. They are a pride of lions who remain loyal to Scar after his death. Because of their ties to his tyrannical uncle, Simba banishes them to the Outlands, where they remain until the pride is disbanded, and its members become Pridelanders again.