Michael and Juno are genetically engineered human weapons from the planet Sirus One . They are also lovers (and not actual twins nor even related to each other). Michael has the power of order, and Juno has the power of disorder. Separately, they are powerful, but together they cancel their powers out.
When they were sent to Earth, they were originally assigned to test their powers in combat against E-Man and Nova Kane and then report back to The Brain, a leader of Sirus One. In combat, they badly hurt Nova, and with that success, they left Earth. However, The Brain however was not happy; instead, it wanted E-Man dead, and it told them that Juno had the power to kill E-man by scattering his atoms across the universe. Juno didn't want to do it, but it was the only way for the twins to go home, so they agreed. On their way to kill E-Man, they were intercepted by E-Man himself, who changed their powers so that when they are apart they are weak but if they get together they will scatter their own atoms across the universe. Thus E-Man left them in tragedy.
Eventually the Twins repented for their crime, and E-Man restored them to normal.