Sonic Underground

Queen Aleena, the former ruler of Mobius, was overthrown by Dr. Robotnik and his lackeys Sleet and Dingo. Robotnik seized control of the planet and forced Queen Aleena into hiding. To preserve the dynasty, Queen Aleena separated her three children: Sonic, Manic, and Sonia after the Oracle of Delphius told her of a prophecy, proclaiming that one day, Queen Aleena would reunite with her children to form the "Council of Four," and overthrow Robotnik. Meanwhile, Dr. Robotnik did his best to set up an autocratic government, and legally turned anyone who stood against him into robots devoid of freewill, and forced the nobles into paying large amounts of money to him as tribute.

(Source: Wikipedia)