After Omni-man (Nolan Grayson), Invincible's father was revealed to have killed the Guardians of the Globe, he left the planet for deep space. Some time later his son had discovered his father on an alien planet (where the insect like locals age faster than humans, their average life span being about nine months) with a new wife and child. The planet is soon attacked by Viltrumites, and Invincible and Nolan are forced to fight the Viltrumites. Nolan is captured by the Viltrumites after the battle is over. The Viltrumtes give Invincible his father's mission of taking over Earth and give him a hundred years to do it. the boy's mother Andressa told Mark to take his brother back to Earth as she wants to stay behind and rebuild her planet with her people. When Mark returns his mother is happy to take care of the boy and names him Oliver. Due to Oliver's insect DNA he ages faster than Nolan and has begun to show powers like his father.
Life On Earth
When Mark returned his little brother to earth, things began to happen rather quickly. Young Oliver is given a legal ID and a tutor who is skilled enough to handle his accelerated learning. As he got older, his brother began to train him. And, when he was old enough, his brother got him a real costume.
After the costume, Kid Omni-Man found it hard to restrain himself. Even when Invincible told his brother to hold back, Kid Omni-Man usually ran head first into the fight. His early attempts in battle went pretty roughly, but that didn't quench his eagerness to be in the fights.
When Invincible flew off to fight the Mauler Twins as they attempted to take over a nuclear facility, Oliver tagged along. Invincible tried to get him to leave, but the missiles within the facility where launched, and Invincible had to go after them. In his absence, Kid Omni-Man violently killed both of them, swearing later that it was an accident.
But was it? Oliver has shown several times over that he feels very little sympathy for the human condition. He has openly voiced that he doesn't not consider humans to be "his people", and that he hates almost all of them. His super-developed ability to learn has out-stripped the development of his morals, giving him all the knowledge he needs to rationalize his actions and none of the morality to truly decide what is right and what is wrong.
Kid Omni-man's most recent adventure took place as his brother pre-occupied himself with personal issues. While Mark was away, Oliver donned his costume and went off to face one of Invincible's villains. Though the confrontation wasn't really a fight (the guy needed help from someone strong to help him get out of his suit of armor), there was allot of property damage, and Invincible was angry when he found out.
The story of Kid Omni-Man is still very young, and young Oliver can go to either side. And he may even grow to be more powerful than his brother. Only time will tell.
When Conquest arrives on Earth, Oliver tries to help Mark fight off Conquest, but is toss aside by Invincible so he doesn't get hurt. Oliver comes back and kicks Conquest in the face, but Conquest gets up and hits him in the face and dislocates his arm and proceeds on to kill him, only to be stopped by Invincible. After the Conquest battle, Mark and Oliver are seen in an hospital talking about what has happened. Mark then admits that the only way to get rid of badguys is to kill them.
We later see Oliver with a new costume and a new name, now calling himself Young Omni-Man. After his father came back to earth, recuting Invincible and tech Jacket, Oliver wanted to go with them, but refused saying that he was needed on earth. But Nolan told Oliver that he should come, because they have a lot of catching up to do. In space they are attacked by Conquest and 2 other viltrumites. As the fight, Oliver loses oxygen and is forced to go to a close planet to regain his breath.
Conquest follows Oliver, but he is struck down by Mark. Later on, both Nolan and Oliver find a near death Invincible after his battle with Conquest, killing Conquest once and for all. A couple of months pass until Mark finally recover from his wounds and the 3 of them head out to help the others.
After some time everyone head to space to fight the remaining viltrumites and Oliver is seemingly killed by Thragg. It is later revealed that Oliver is indeed alive and its recovering. He was left to recover.
Oliver, while working as a double agent for Allen in gaining Thragg's trust, was ordered by Thragg to not interfere in his assault on Mark's family to prove his loyalty to the Viltrumite cause. Oliver disobeys Thragg's orders and attacks Thragg to protect his niece, Terra Grayson. During their skirmish, Oliver angers Thragg after reminding him of his jealousy that he will never be as good as a ruler in comparison to Oliver's Argall related bloodline. This leads to Thragg punching a hole through Oliver's chest, instantly killing him while a shocked Terra asks Thragg whether her uncle was killed by Thragg in disbelief.
Due to Oliver's hybrid alien DNA he ages faster than a Viltrumite, but Nolan believed that as he matured his Viltrumite powers would awaken and he would age slower. This has proven true as Oliver has demonstrated flight, strength and invulnerability. He also seems to have stayed in his teenage years. Oliver also has the powers of his race, which give him a perfect memory of everything he's ever seen or heard going all the way back to birth.