Lui was once nice like the others, but it changed when his mother died, and him and his sister, Claire, had to deal with his alcoholic father. Their dad would abouse them for not getting a chore done, or not getting him a beer, or just because they were alive. Their dad would usually target Claire, but Lui always protected her. So Lui may seem like a jerk, but don't blame him, blame his dad. 

Kerindia: IT'S STILL NO REASON TO-

Author: Quiet child *puts duct tape on her mouth* 

Lui: ... *looks down* Yes, dad...dad abuses Claire and I, but I take most of it because Claire doesn't deserve any of it.

Claire: Neither do you....

Lui: ...