Castiel is an angel and a warrior of God. He was taught total obedience to hierarchy of Heaven. Living... sometimes in Heaven and sometimes on Earth. Can be quiet and reserved, almost robotic. Castiel is a strong, determined, impulsive, competitive and naïve celestial being. Like most angels, Castiel expresses little to no emotion, which creates flaws and complexities in his persona.
Sam possess 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 does not seem to drink alcohol as much as Dean does and has a much healthier diet than his brother. Hunts the supernatural with his older brother, Dean.
..Not very similar.
But, they make a wonderful bromance. Kinda. Their just super silly. And lovey. They might was well just be dating at this point. They are. In secret.
Cas also, DOES NOT HAVE GAMES ON HIS PHONE.
Cas: "Sam! Stop asking me that!"
Sam: "Do you? Do you have games on your phone!?"
Cas: "No!"
Sam: "Awhh.."
Castiel thinks it's finally over.
Sam: "Do you have ga-"
Castiel shuts him up with a kiss.
Cas: "No, Sam."