Talk to his parents or something.
His parents originally were trying to make a "genius kid" out of him, needless to say after about 14 1/2 years of ADHD medication, intense stress of being sent to a school for gifted children for a few years until he flunked out, and perhaps physical abuse (heard and saw lots of things involving his parents beating him), leaving him with very little social skills, and turning him into a perhaps clinically insane shell of a person with very little personality.
I think that explains that his parents don't give two stuffs about him, or his sister (who may or may not be normal).