After Zeus found out that his father and all his monsters had been released he immediately called a meeting of the council (the main Gods and Goddesses), he also called King Mickey to the meeting.
Before the meeting began Zeus had something he needed to get done. Zeus journeyed into the realm of darkness and pulled the Organization out of the darkness and brought them back to life. They were still nobodies but they were alive, in their own non-existing way.
Zeus took Xemnas with him to the council and the made an alliance; as long as this new threat stood the Nobodies would ally themselves with the warriors of the light.
And so the lines have been drawn.
((If you're RPing as King Mickey or Xemnas you have to include something about this in your profile.))