Kobato includes characters from Chobits and Angelic Layer, as well as other CLAMP series, in its world. But it doesn't seem to be the same world as Chobits and Angelic Layer; for example, Chitose Hibiya's children don't appear to be persocoms.
Does Kobato take place in the same world as any other CLAMP series, or is it a standalone world that includes alternate versions of some characters?
(I haven't finished the series, so please use spoiler tags liberally.)