The name Children is an informal name given to the collective of individuals who follow Elizabeth Borden in her exploits. They are not always mutants, but the majority of them are. They work for Elizabeth Borden due to her end goal, which is the consolidation of power under her banner. They have shown loyalty to her, even when they work with other organizations, which is a key component of how they acquire power.
Due to personal reasons, they are all in direct confrontation with Massachusetts Academy. The most prevalent reason is the personal animosity between Elizabeth Borden and the leader of the Academy, Alessandra Santiago.