Astarion's past before Cazador was cut and they didn't give him a new one. Cazador related stuff changed too. That might be why there's nothing in his origin and why the narrator says things that don't make sense sometimes, like "your master's coven is close to Baldur's Gate" when the palace is in the middle of the city, or how sunlight on his skin feels like "a caress of a lover who doesn't know better yet". 5 patches and they haven't figured out that maybe they shouldn't imply that he enjoyed being used that way.
