There are in fact two Sub-Zeros: older and younger. Both are blue garbed warriors (assassins, but not "ninjas", since the Lin Kuei are Chinese despite being called ninjas in several Mortal Kombat games) that descended from Cryomancers, an Outworld race possessing the ability to generate and control the powers of ice, although both of them were born in Earthrealm. The younger one bears a conspicuous scar on his right eye, however, as of Deception the scar has faded away. The Elder Sub-Zero appeared in the first Mortal Kombat and then, after being killed by Scorpion, his younger brother replaced him for the rest of the games- his elder brother later became the undead Netherealm wraith, Noob Saibot.

The younger Sub-Zero clearly shares many traits with his older brother. Upon his introduction, the younger Sub-Zero was perhaps too similar to his brother. Like the elder, the younger Sub-Zero gives the impression of being a stern, distant and cold man who goes about his business silently, without attracting unwanted attention. However, as time progressed, Sub-Zero evolved from what fans labeled a "carbon copy" of his brother to a man of great integrity and self-discipline. The disparities between the brothers, who were once neutral and almost indistinct from each other, have now grown so large that one could speak of the evil twin syndrome.

While the younger Sub-Zero was depicted as a young Lin Kuei warrior who was living in the shadow of his older brother, he has since changed and grown into a warrior who has progressed towards the more humane sides of moral issues. This change in characteristics has not only strengthened him as a man, but has also set him apart from his former Lin Kuei counterparts. This included leaving his clan in disgust and breaking the sacred codes of honor, joining the rebellion against Shao Kahn and assisting Raiden and Liu Kang (along with Earthrealm's other chosen warriors). More recently, he defeated the cyborg assassin Sektor to gain the leadership of the Lin Kuei and become the Grandmaster, where he has grown even stronger and more powerful. He is a dependable ally of Earthrealm who is willing to assist when needed, especially when Raiden gives the call.

Younger Sub-Zero is easily identified by the scar on his face which, according to Mortal Kombat: Shaolin Monks, was caused by Kung Lao, who sliced Sub-Zero's face with his hat when he mistook him for his older brother (although this event may or may not be canon).