Hamato sons

The Hamato Sons were the four human sons of Hamato Yoshi and Tang Shen, and the previous incarnations of the Ninja Turtles who lived in feudal Japan. The story has never specified their individual names.

As small children, they briefly encountered their future incarnations when the Turtles were accidentally sent back in time and were mistaken for demons. Shortly thereafter, Oroku Saki ordered for Yoshi and his family to be executed, and Shen died attempting to protect her children from assassins. Her dying request was for Yoshi to keep their sons safe rather than seeking vengeance, and so he fled with the four boys into the night. 

Eleven years passed, during which the Hamato sons were taught the use of various ninja weapons in a remote mountainous area. Saki eventually found them, and Yoshi was forced to watch as his sons were murdered in front of him, shortly before his own death.