Sam possesses a dual nature. He can be unusually kind, empathetic, intelligent and independent. But he can also be coldly pragmatic, cruel, vengeful, arrogant, and proud. Sam tends to be driven by feelings of anger and vengeance. It is only through constant, deliberate choice that Sam develops his better qualities and rejects his darker side. he is described as 'sweet, brave, selfless Sam'. He is often the exasperated voice of logic in his relationship with Dean, who in turn sees him as a geek or prude, and teasingly calls him "bitch," to which Sam usually responds with "jerk". Dean has respect for Sam as a capable hunter and trusts Sam to "have his six".

Dean Winchester, from the moment of his debut, was shown to be an understanding, funny, mischievous, and, in contrast to his younger brother, a little immature. Dean's shown countless times to be good with kids and the ladies. At an early age, Dean was trained by his father, John Winchester, to hunt and kill creatures of the supernatural. However, unlike his brother Sam, he did not resent his father for having him "raised like a warrior". He seemed to prefer hunting the supernatural over any normal "apple pie" life, though it was revealed that when he was sixteen, he did in fact desire (or at least hope for) a normal life: he just couldn't leave Sam. This however did not last long, as later on - while still sixteen - following a werewolf hunt, he realized just how unique his life was.