Catwoman, distracted by the loss of Bruce Wayne, was taken down in Gotham city by Boneblaster, a new super villain trying to make a name for himself by killing big name vigilantes. Due to her recent encounter with Hush, Selina was not herself in peak physical condition. She was saved by Poison Ivy, who then brought Selina back to her hideout, which was actually the apartment of the Riddler, whom was being drugged by Ivy. Harley Quinn is also living there with Ivy. When Boneblaster attacks again, having followed them to the general area, and then locating the house with plants. After the tree ladie defeated Blaster (leaving him to be beaten by the Riddler, whom he had also attempted to kill) Selina suggests they form a team. After a consult with Zatanna to find out what was really wrong with Catwoman, Poison Ivy and Harley Quinn agreed as, "positive female reinforcement", but then asked a simple question to Ms. Kyle who is Batman? Ordinarily, Catwoman would have refused, but she was being forced to tell the truth by toxic plants wielded by Ivy. Using skills taught by Talia al Ghul, Selina was able to convince them stating that everyone who had ever taken the cowl and pretending that is was a league of Batmen. Quinn and Ivy were satisfied, and accepted heroffer of a team.
The trio are known for being part of batman's rouge gallery of villains. While the trio are still considered to be criminals, they engage into hero activity from time to time.
A short animated flash and comic series of the Gotham Sirens. This flash series does have Batman. Instead of Batman Batgirl is the hero in the series.
Gotham Girls is another name for the team.
Never in all Arkham games have the Gotham Sirens worked together as a trio. However, in the Arkham Unhinged comic book series they have.