Sasuke was born on July 23 from Fugaku and Mikoto, he had an older brother named Itachi, bigger than of him seven years.
He is also the second born of the chief of the Konoha Military Police Force Fugaku Uchiha, and his wife Mikoto Uchiha, members of the Uchiha clan who founded the Hidden Leaf Village alongside the Senju clan generations ago.
He was named after the father of the Third Hokage, as his mother hoped he would grow up to be a fine shinobi like his namesake.
While he was only a newborn, Sasuke was in the care of his older brother Itachi Uchiha as they saw the attack of the village by Kurama the Nine Tailed Fox, only with Sasuke sensing the demon’s evil chakara which frightened him. That event, due to the fact that only a Uchiha could control the Tailed Beast, ultimately led to their clan losing complete standing.
As a child and unaware of the events that revolved on his clan, Sasuke was more focused on becoming like Itachi, who had their father’s favor, and trained to become strong. However, when Itachi began to distance himself from the Uchiha Clan, Sasuke found himself getting Fugaku’s attention as he taught Sasuke their clan’s Fireball Jutsu which the boy spend days to master before being told not to follow in Itachi’s footsteps.
One evening, coming home from practicing his ninjutsu, shrugging off the feeling that someone was watching him, Sasuke found the area surrounding his home littered with dead bodies of Uchiha Clan members. Frightened and confused, Sasuke ran to his home to find his parents killed by Itachi’s hand. Freaking out as he yells at Itachi at what he was doing, Sasuke finds his left shoulder wounded as he is subjected to Itachi’s Tsukuyomi playing the slaughter Itachi committing. Itachi then tells Sasuke that he spared him because he is weak, telling his brother of obtain the Sharingan in Mangekyo form and live a life of hatred before facing him again. As Itachi leaves, giving him the location of their clan’s vital documents, enraged Sasuke caused his Sharingan to manifest as he attempts to kill his brother. However, Itachi overpowered Sasuke and he ended up in a coma for a few days.
With the events hazy, due to his brother’s genjutsu, Sasuke had no memory of obtaining the Sharingan. After mourning over his clan’s death and discovering the secret documents on the stone tablets, Sasuke swore to avenge his clan and kill Itachi by any means. Since then, Sasuke has become a loner and kept to himself most of the time. While attending the Ninja Academy a few years later, Sasuke encountered a similar social misfit, Naruto Uzumaki. Since that meeting, Naruto recognizing the festering darkness in Sasuke’s eyes and the two had become destined rivals.
When he was a child, Sasuke was very kind, loving towards his parents and older brother and respectful to his fellow clansmen as well as his teachers. He was even very proud of being Itachi’s younger brother and the youngest son Fugaku and Mikoto — famous for being devoted protectors of Konoha, and he desired to emulate them. His original dream was to join the Konoha Military Police Force when he grew up, like his father and as such greatly sought his father’s approval and acknowledgement of his abilities. After Itachi massacred the clan, Sasuke’s ideals and personality changed drastically due to him suffering his clan’s curse and became cold, indifferent, cruel, cynical, callous, somewhat arrogant, unreasonable and devoted the next nine years of his life to kill Itachi.