i dunno.
(i think) in M2 when neo talks to oracle she talks about programs who dont behave like they should - and this explains why normal people in the matrix see things like angels,ghosts etc.
then the characters illustrate this
Persephone is a type of vampire
her guard that she shoots with silver bullets are types of werewolves
therefore the twins dont behave like they should and so are 'types' of ghosts. (not living people who died - that is our perception of ghosts. but what ghosts really are - programs doing stuff they shouldnt)
PS i though it was a nice touch in M2 when the 'werewolves' are watching some sort of horror film - anyone know what film that was?