Actually, I believe Knuckles is really Sonic's older brother. Uncle Chuck never told Sonic this because Sonic's mother was sleeping around and wasn't exactly a pillar of moral character. Sonic's father got so upset that he tried to kill her with a mallet, but Uncle Chuck stopped him, and invented the Power Rings to symbolize the love between water and fire.

This is relevant because Knuckles has a twin named Knuckles and that was really the Knuckles that was being stuff. And Dr. Robotnik isn't really a doctor, he never got a degree from any college or anything. I would say he's more of a crazy person or something.