It is based on the story of a telepathically-linked Romulus and Remus from Virgil’s Aeneid. It has no relation to the 1927 movie Metropolis.
Petrucci wrote it as a sort of fantasy epic, inspired by the likes of Yes and Rush. The story itself is original (the twins are named Miracle and Sleeper and do not appear in literature) but the story type was Homeric.
It is linked to part 2 (Scenes From a Memory) in that Edward and Julian Baynes are metaphors for Romulus and Remus, and Victoria is a metaphor Rome (or the ‘Metropolis’). This is supported by several lyrical lines in Scenes From a Memory.