Actually, real life isn't naming exoplanets I, II, II, etc., except in fiction.
IAU naming conventions (
explained in detail here) assign lower case letters, starting with
b, to exoplanets orbiting a star in the order of their discovery, not their position relative to the star. Take the star
55 Cancri for example.
The order of discovery was b, c, d, e, and f, obviously, but the order from the star is e, b, c, f, d.
(
Image showing the four inner planets of 55 Cancri compared to the Solar System)
edit: fixed an awkward sentence.