A: Depending on what you mean it is either:
1. referring to the excerpt of journal of the whills foudn in the beginning of star wars ANH first draft(a.k.a. Adventures of the Star Killer), or Star Wars ANH novel.
2. referring to the prophesy written in the journal of the whills, specifying that the chosen one will be born on Tatooine (which orbits a binary solar system)
For fun, I'm going to go with #2. Son of the suns means the chosen one (who will bring balance to the force), will be born on tatooine.
Not sure if I'm correct. pass either way