22 years ago - Eddie Bloomberg is born.
10 years ago - 12-year-old Eddie is saved from the demon Nimbos by Dan Cassidy who becomes Blue Devil.
7 years ago - 15-year-old Eddie dies in a car accident. He makes a deal with Nimbos, the same demon that cursed Dan Cassidy, to be allowed to return as a demonic agent if he agrees to serve the demon upon his actual death, becoming Kid Devil.
6 years ago - 16-year-old Eddie joins Flamebird's Titans, and dies during the bombing of Quroc. Dan Cassidy travels into hell and offers to change his allegiance to Etrigan if the demon will free Eddie's soul from Nimbos.
Kid Devil was conceived as a part of Blue Devil's original run with it's focus on humor. He was a powerless kid that used a few technological tools to help Blue Devil fight crime, and looked for all the world like the Great Gazoo. He disappeared, and was not missed.
When he resurfaced, he had been re-purposed with a fantastic look and great devil-based powers, a character being dredged up from obscurity to flesh out a teen titans team whose membership had been needlessly decimated in one of DC's Crisis. They barely had a idea in mind to explain his new look, and scrambled to fill in his backstory to make it work, but that was hard when his own mentor character's backstory was less than stellar. So why keep him? because he's a cool character. Look at him. Metal.
He actually fits neatly into Blue Devil's early career, but for that to mesh with the Teen Titans timeline he can't be a modern member. He actually becomes a perfect fit for Flamebird's doomed team... and the fact that he's so likable suggests that me might be the very first to die. His ultimate fate is an important story for Dan, so including his death actually bridges the two stories quite well.