Tobio Tenma was the young son of Dr. Tenma and Hoshie Tenma, often put aside by his father in favor of his work. But after he was killed in a tragic accident, Dr. Tenma created a robot to replace his deceased son. That robot was Astro Boy. Not much is known about Tobio's mother, she died when Tobio was little and Tobio didn't remember her very well. However, in the Manga chapter 18, they changed this, and made Tobio's mother an important part of Astro Boys development into a robot that behaved and acted like Tobio!
In the manga Tobio is shown in the first few pages before being killed off in a car accident, his backstory was somewhat expanded upon in chapter 17, "Once Upon a Time". Where it's revealed that the car he was driving was a toy car Dr. Tenma brought him, which Tobio decided to take onto the road.
1960's TV series
Tobio is seen in the first episode, going for a joyride in his father's automobile. though he was allowed because in the futuristic year of 2000, driving a car was completely safe, all Tobio had to do was press a button, but there was a terrible malfunction. Tobio is involved in a horrible car accident and is killed. When Dr. Tenma heard about this, he came to the site of the accident in tears and held Tobio's dead body in his arms. After this Dr. Tenma falls into a state of deep depression but he later creates a robot that looks like Tobio, that robot is Astro Boy. Tenma treated Astro Boy as if he were his real human son and loved him like he was his real son but later abandons Astro at a robot circus after realizing he was not his real son.
1980's TV seriesIn this series the story is somewhat different, it begins with Tobio going to see his father at the Ministry of Science, instead of Tobio driving in an automobile. Tobio wants his father to drive him to the amusement park. Dr. Tenma neglects Tobio and says he is too busy for him right now, Tobio is hurt by this and leaves the ministry to drive the car by himself. He is too young to drive and is inexperienced, his driving goes out of control and he accidentally crashes into a truck and is killed. Dr. Tenma mourns the loss of his beloved son. Like in every version of the show, he creates Astro Boy. In this version. he did not abandon Astro he was separated from him while on a cruise ship.
2003 TV seriesIn this version, Tobio is highly neglected, as his father is always busy. Dr. Tenma is always missing important moments in Tobio's life, Tobio misses his father and is hurt when he wants his father to see him doing something he deems as important. Tobio was close friends with a robot tutor that Tenma had built to educate him. But after a new model was released, Tenma deactivated that robot to build the newer model, and Tobio became upset with his father about this. While Tenma and Tobio were at the ministry they had an argument about this and Tobio ran from his father and rode on his new jet bike that his father chased him until he crashed into oncoming traffic inside a tunnel. After his death, Tenma was heart broken and blamed himself for his son's death, but then he created Astro Boy. Dr. Tenma went insane sometime after this and deactivates Astro along with his other robots. Astro Boy is later recovered and reactivated by Dr. Ochanomizu
Toby, after sneaking into the room where Dr. Tenma and Ochanomizu were demonstrating 'The Peacekeeper' using the power of blue and red cores, is soon trapped behind an emergency glass separating the scientist from danger. But is soon killed when 'The Peacekeeper' unleashes a deadly force to destroy the glass shield.