The Forgotten Ones

Juno Thalia, Pluto Nikoli (Nico), and Neptune Perseus (Percy) are the twin brothers and sister of the big three. Perseus and Poseidon, Thalia and Zeus, Hades and Nikoli. however, as the Romans are getting the upper hand of ancient Greece they were banished to Tartarus by their family for being too powerful. now they appear again during the 2nd titan's war.
Where have they been all this time?
who will they aid?
will the Olympians try to banish them again?
read and find out.

(note: this is sort of a crossover with Nightschool by svetlana, however, you can read this without having to read the nightschool series)

**disclaimer** no, I'm not Rick Riordan