Long after the death of the Z warriors earth is left defenseless from the merciless perils of the dragon-ball universe. In a attempt to protect the planet, capsule corp utilized the data left by doctor Gero and Friezas army to artificially create enhanced super soldiers called bio saiyajins.
Having only enough genetic material to craft seven warriors the reluctant scientists of capsule corp began the endeavor. However the science alone was not enough using the power of the dragon balls they imbued their genetic warriors with life and knowledge.
The first to be awoken and perfected was 7 a powerful bio saiyajin warrior for years he alone defended earth from danger. However the loneliness and constant fighting took their toll on him and he soon grew obsessed with his genetic originals. The more he fought the more his saiyajin blood cried for more violence and combat. To prove his superiority and to test his skills he began working in secret, experimenting on himself using the data and records from the past.
7's creators sensing something was amiss woke up his younger brothers 6,2 and 4. The four warriors worked in tandem protecting earth and their galaxy. It wasn't long before the four warriors made a name for themselves across the stars. They became the most feared and respected entities in the known universe, policing the galaxy and protecting those charged in their care. However all was not as it seemed. 7 hungered for more and being at the top bored him and his thirst for battle. He soon became more and more aggressive in his missions.
It wasn't long before the humans of earth began to fear their protectors seeing them as monsters. They were despised and capsule corp stocks had taken a massive hit because of it. Seeking to curb the public's fear and save their company capsule corp seek to embed power limiters in their creations.
Word quickly got out that the bio saiyajins were weakened and all the enemies of the universe gathered attacking the earth at once. After a long hard battle and many losses 7 had lost it blaming his weak human creators for the mess they had caused. After secretly removing his limiter he turned on his creators attacking humans in an attempt at subjugating them and conquering the planet.
Many humans escaped leaving their home world to settle among the stars. In an attempt to defeat 7 the surviving capsule corp scientists woke up the remaining bio saiyajins. 3 and a partially completed 1 joined the battle against their eldest brother. However 7 was too strong. 1 being the strongest and most powerful among his brothers engaged 7 alone but severely wounded himself in the process along with his twisted elder brother.
7 sensing his defeat decided to escape earth and carve out a new empire in the vast corners of space. 2 in awe of his older brothers power and battle ability stole the corpse of their brother 4 and joined 7 leaving earth forever.
6,3 and 1 were left to help rebuild and the long war of the bio saiyajins had ended.