Damien is the Son Of Batman.

Talia, Daughter of Ras Al Ghul, the Demon's Head; Drugged him and raped him while he was semi conscious. Years later, after he been raised by the League of Assassins, Talia Drops him off at the Batcave and lets Bruce in on the secret. He goes back to the League briefly, but when the newly resurrected but terribly malformed Ras Al Ghul expects him to surrender his existence to serve as a vessel for Ras' Consciousness, Damien leaves never to return.

Dick Has Made him Robin, because he fears what he might become without the proper guidance.

This was all covered in the Grant Morrison Run on Batman following Infinite Crisis. (and resolving now in the new Batman & Robin series, which is awesome)