Samuel "Sam" William Winchester (born May 2, 1983) is a hunter as well as a Man of Letters, along with his older brother Dean. He is one of the main protagonists of Supernatural. Both Sam and Dean are related to the Winchester and Campbell families - a Letters family and a Hunting family respectively. The pair also share a bloodline with Cain and Abel. Because of this, Sam was predestined to be the true vessel of the fallen archangel Lucifer (whilst Dean was Michael's). Sam is friends with angel Castiel, Prophet Kevin Tran, the demon Meg and former lover-turned-enemy of demon Ruby. He is also the occasional reluctant ally of demon Crowley and for a time was forced to be an unknowing and unwilling vessel for the angel Gadreel (before expelling him).

After the demon Azazel killed their mother, Mary, both Sam and Dean were raised in the hunting life by their father John. Sam left the hunting life to pursue a career in law, and most likely would have married his college sweetheart Jessica Moore. At the series' start, Sam was reluctant to start hunting again. When Jessica was killed, he was pushed back into the hunting life. However, he has been repeatedly known to try and back out of hunting in the hope of finally having a normal life as he wanted.

Sam is very mentally strong, evidenced by his ability to overpower possession by Lucifer. It has been argued that he is the smarter or more intelligent of the Winchester brothers, although Sam himself would disagree.

Over time, Sam has resigned himself to the hunting lifestyle and has repeatedly sacrificed himself for the greater good, highlighting his selfless nature.

Dean Winchester (born January 24, 1979) is a human and hunter as well as a member of the Men of Letters with his younger brother Sam. He and his brother are members of the Winchester and Campbell families, and Dean is also the destined vessel of the archangel Michael[1]. He and Sam are also the surrogate sons of Bobby Singer. Dean is best friends with the angel Castiel, close friend to the late prophet Kevin Tran, and reluctant ally of Crowley. Dean has an ex-girlfriend, Lisa Braeden who he lived with for a year when he thought Sam was in Hell. She has a child named Ben, who Dean acted as a father for during that year. Dean is also the former apprentice of Alastair.

Both Dean and Sam were raised in the hunting life by their father, after the demon Azazel killed their mother. Dean's main role in the series is being the self-appointed guardian of Sam and often going to extreme lengths to protect him regardless of personal cost. Often in these occurrences Dean finds himself the center of a much larger picture.

When he was killed by Metatron whilst using the Mark of Cain, Dean returned as a demon and a Knight of Hell loyal only to himself. He was then cured by his brother using purified blood. Eventually, the Mark was removed, but the price was that the Darkness has now been released into the world, something Dean tried to avoid.