He was born into a poor family to two firebending parents, in a small village located in the Fire Nation. There wasn’t much story behind them, just like there isn’t much behind him. They were reclusive people and often kept to themselves. He discovered his bending at an average age of six - the discovery nothing special. His parents didn’t care whether or not he was a bender, they only cared about his health and happiness. His father decided to be the one to train him in the art of firebending. It wasn’t fancy, but it was still knowledgeable, and helped him a lot in the long run.
His parents, whom he adored so much, were ripped away from him at the young age of nine. They couldn’t pay the landlord and so a sadistic man burned their home to the ground out of spite and drunken anger for a lack of income on his behalf because of the small family. It was the middle of the night and only Tae was able to escape from the burning building. The irony, two firebenders dying in a fire. Somehow the landlord was able to avoid the authorities, because he was the authority. He was a wealthy man who owned large sections of the village, often abusing his power among the people to benefit himself. He cared little of the other lives of those who resided under him.
Tae was left to live with an elderly woman, who was only willing to take him in, if he worked for his feed. She, like his parents, owned a small farm; so the work wasn’t a hassle for him. She’d give him enough money for clothes and treats, though it was a rare gift, he still managed to save it. He needed to accumulate enough money, so he can escape the corrupt village, and move to a place that promised equality for all.
That city, was Republic City, and Tae was lucky enough to find an unguarded ship heading there. Without notifying anyone, he left with a small bag of money and the clothes on his back, as a stowaway on that ship. Once he reached Republic City, he took on the surname “Yang”, ignoring the social norms that said a surname was only for the rich.
This caused him to go through a reality check, people mocking him and belittling him for his naivety. He witnessed the cruelty and corruption within Republic City, up close and personal, finally allowing him to realize that this was the world. The way the city worked reminded him of his wretched home, and the evil man who took his parents from him; it made him want to take down the rich and snobbish people that created the corrupted place. It made him join Koh’s Entropy.