There are currently a total of 2 Pokémon in the Rattata (Alola Form) family. Rattata (Alola Form) evolves into Raticate (Alola Form) which costs 25 Candy.
There is a very low chance that you can get a shiny Rattata - Alola Form, which has the following appearance:
About
"Rattata is cautious in the extreme. Even while it is asleep, it constantly listens by moving its ears around. It is not picky about where it lives—it will make its nest anywhere."