How often have you seen brothers and sisters that are totally different. I personally know of brothers who are different ends of the spectrum, One just an asshole to everyone including family constantly in trouble with law and fighting everywhere. The other is pleasant prob never even drives over the speed limit, and would do anything for you. These guys are like 1 maybe 2 years apart so the whole upbringing couldnt have been too different.

I think people use the whole upbringing thing as an excuse as to why they treat people like shit. Some people are just not nice people and thats they way its always gonna be.