I read this fanfiction a while ago on fanfiction.net and I don't remember what it is called.
Main character is called James, and while he is on Earth he is taken by a Sith (Count Dooku I think, and he kills the boy's family) but then the Jedi arrive and he fights Ahsoka and wins and I think he goes with the Jedi. The villain uses the power of a Kyber Crystal. MC then defeats Darth Sidious. Later on the MC meets another Sith who was in a group with Sidious, and also came from Earth, but 10 years before, and he beats the MC really badly. This new Sith also uses the power of the same Kyber Crystal, but much more effectively, and the MC uses the Dark Side to win after the Sith threatens Ahsoka her child (she's pregnant).
I think his last name might be Brown.
Darth Sidious and the other newer Sith were both Commanders(?) and the main characters were looking for a "High Commander".
The other Sith was trying to capture Mara Jade and the main characters adopted her because her parents were dead.
He once gets trapped in his own ship by his troops and all the lights turn off and his lightsabers get taken from him and they use a machine that takes the force away temporarily. He kills three soldiers and uses their guns to take down the commander who went bad. He then meets a Yuuzhan Vong, who gets killed by the commander who uses a snake staff.
He calls himself Blaze.
The main character's catch-phrase is:
forever and always
