Is Sub-Zero Scorpion's Brother?
The various Mortal Kombat timelines are confusing to say the least. There are characters dying, characters being brought back to life, and even some roles that have been filled by multiple fighters. We can understand, then, how players can get tripped up, as they routinely do around the characters of Sub-Zero and Scorpion.
Is Sub-Zero Scorpion's brother? No, the two are not related in any way, shape, or form. But the term "brothers" does come up in material referencing the two, and there's a reason for that.
As we stated earlier, there are instances where multiple fighters have used the same Mortal Kombat character name. Sub-Zero is one of those characters. He was originally Bi-Han, a Lin Kuei assassin who was killed by Scorpion during the first Mortal Kombat tournament. But as you might have noticed, Sub-Zero didn't disappear from the MK universe. That's because Kuai Liang — Bi-Han's younger brother — carried the look and name used by his brother forward, even learning cryomancy in order to fully become the next Sub-Zero.
The Kuai Liang version of Sub-Zero vowed to exact revenge on Scorpion for murdering his older brother, but when the next Mortal Kombat tournament rolled around and Scorpion learned that the new Sub-Zero was actually the younger brother of the man he killed, he swore to protect him rather than fight him. Who knew resurrected assassins had honor?
Anyway, that's how some might come to be confused about the connection between Sub-Zero and Scorpion. The two are not brothers, but the two versions of Sub-Zero were. Scorpion killed one of those Sub-Zeroes and — in accordance with some kind of ninja code — promised he would protect the second Sub-Zero rather than kill him, too.
It might not make a whole lot of sense in the grand scheme of things; then again, there's a whole lot of Mortal Kombat lore you could say the same about.