Ever since he was a kid he was solitary and at kindergarten he had one or two panic attacks (I remember my mother said he was yelling something like 'I am not [his name]', I'M NOT [his name]!!) but that could be just a stage of growing up maybe?
He never made friends later and the few he had he quarrelled with them and never saw them again. During middle and high school he never had any friends and never had a relationship, he decided to go to a military school (I'm pretty sure, just to follow my father's journey) and he wasn't not even a bit sociable there. He has been with a prostitute at the age of 18 because he couldn't find a person (my father helped him finding the prostitute), now he's 25 and didn't make any friend yet.. he works but he hates his job (the same as my father's)..
When he talks about himself he constantly act like a martyr and blame my parents or others for anything that happens to him (sometimes it may be true, but not always as he says, obviously)..
I was reading about autism, sociopathy and psychopathy and I'm sure he fits in one of the descriptions of those disorders :\ or probably my father's a psychopath controlling him :|