(I don't own the rights to any of these characters I'm just a fan making a story, I will be using characters and things from other comic book franchise like Marvel comics, Image comics, WildStorm Comics and The Boys as well as I may use the names of characters, backstories and things within this story)
Earth 21: Superman's origins
There was once a peaceful world that was known as Krypton which was the home world for a technology advance race called the Kryptonian's who were they known as one of most advanced civilization in the known universe and they were governed by the Ruling Council and their society was different from many other races in the Universe as unlike other races Kryptonian's are not born though natural means instead they are created in the Birthing Matrix which was a chamber where Kryptonian children are artificially created and they are raised in separate from their parents until they reach a certain age.
Krypton had always had a bad relationship with the Dheronian's who were from the world known as Dheron which was a nearby planet to Krypton and they have hated each other simply because of their various differences, such as Democracy vs Monarchy and how life should be lived which eventually led to a war between the two world's.
The war between Krypton and Dheron lasted for many years with casualties between the two world's were in the thousands which cause both the Ruling Council of Krypton and the monarchy of Dheron to finally call a end to the war however not everyone wanted the war to end because they wish to avenge their fallen friends and family like General Dru-Zod who was a distinguished soldier in the Kryptonian military like almost every single other member from the well-known and respected House of Zod and he wanted to avenge all of the lives of the Kryptonian's that had been killed by the Dheronian's during the war.
Dru-Zod believed that the current Ruling Council was weak and so that Krypton needed a stronger leadership to led Krypton into becoming a great galactic empire in the Universe which it was destined to be meaning himself and Dru-Zod became even more certain of this when he had discovered that the Ruling Council had a secret weapon that they could have use to completely destroy the Dheronian's and won the war for Krypton at the very beginning of the war against the Dheronian's and the secret weapon was a creature known as Doomsday who possessed unimaginable power and bloodlust.
Many years ago on Krypton there was a civil war that was started by a rebel group calling themselves 'Black Zero' so the house's that were members of Krypton's Science Council like the famous 'House of El' work together to create a weapon to stop Black Zero which led to the creation of Doomsday to put a end to the civil war and protect Krypton. However their creation proved to be to violent to be controlled and to powerful to be destroyed so the Ruling council of Krypton at the time used a device which was created by Val-El call the Phantom Zone Projector which can send anyone or anything to the Phantom Zone an intra-dimensional realm outside the normal space/time continuum which would later become a prison where the Ruling Council would send the worse criminals making Doomsday it's first ever inmate.
The current Ruling Council was too afraid to unleash Doomsday from the Phantom Zone on to Dheronian's fearing that what if they did free Doomsday but they couldn't be able to send him back to the Phantom Zone and the creature may also end up destroying them as well. Dru-Zod gathered everyone who also share in his vision for a grand military government Krypton and they call themselves 'The Sword of Rao' after their Sun-God Rao however the Ruling Council was able to stop to them thanks to the help from Jor-El who was the great grandson of Val-El, one of Krypton's greatest scientists and the former best friend of Dru-Zod.
Afterwards the Ruling Council sentenced Dru-Zod and most of his followers to the Phantom Zone but not before Dru-Zod vowed vengeance and he claimed that they have doomed Krypton as the war had left both Krypton and Dheron defenses weakened and neither of them were prepared when Brainiac came to their world's.
Brainiac was a artificial intelligence from the Planet Colu that was originally called 'C.O.M.P.U.T.O' created by Vril Dox basing the A.I on his own brain patterns and it was designed to gather date and study all forms of life however it went rogue and left the Planet Colu knowing that if it stay it's creator and the other scientists would be able to destroy it and once it left Planet Colu it created itself a spaceship and a physical body which it designed to look like it's creator and gave itself a new name Brainiac and afterwards Brainiac continue it's original mission to gather knowledge which has led it to create a device that can struck cities and people so Brainiac could transportation the small orbs on its Skull Ship so Brainiac could continually study the lifeforms and exterminate them.
Brainiac choose Krypton first simply because it was a bit more weaker then Dheron because of the lost of Dru-Zod and his followers and when Brainiac arrive it chose one of Krypton's three greatest cities known as Kandor to be added to it's collation and sent it's drones to gather everyone who it thought was useful and those who it didn't were killed while Brainiac also hack into every computer system of Krypton to downloaded all of it's knowledge. Once Brainiac was finish it then fired a blast from it's Skull Ship into the Planet's core triggering it's destruction like it has done to every other world it has come to as Brainiac wanted to make the knowledge that it had gathered only available to itself and Brainiac then travel to Dheron to repeat what it had just done.
However a few weeks before Krypton's destruction Jor-El had found out that Brainiac was heading towards his world but when Jor-El try to warn the Ruling Council they simply ignored his pleas for evacuation and later expelled him from Krypton's Science Council so with the little of restores that Jor-El had he was able build a small spaceship and on the day that Brainiac had arrive, Jor-El and his wife Lara Lor-Van sent their baby son Seg-El who was name after Jor-El's father and he was the first Kryptonian to be born though natural means after centuries to world known as Planet Earth. Jor-El had discovered the planet because years ago he had sent out a satellite into space for research and Seg-El would be able to blend in with the inhabitants of Earth who are call Human's as they look identical to Kryptonian's and because Planet Earth had a yellow sun unlike Krypton's which had a red sun there were side effects on Kryptonian Physiology which were that the yellow sun radiation can grant Kryptonian's incredible powers.
Jor-El also made sure that Seg-El would know about his family's legacy by giving him a special Crystal which could transform into a large fortress that contained many of Kryptonian technologies and a special orb which Jor-El had originally created for the Ruling Council back during the war against Dheron with it purpose being able to contain a large amount of knowledge as the Ruling Council had intended to use it to copy all of Dheron's knowledge to use against them but instead Jor-El had use it to copy all of Krypton's knowledge before Brainiac downloaded it into itself.
However unlike his counterparts in other Universes everything that happen on Krypton happened far sooner and everyone that was there existed far sooner as well meaning Seg-El's spaceship arrived on the planet Earth in 1922 where it landed in the United States of America near a seacoast town where Seg-El was found by Chester and Betty Sampson who were hiking through the forests when they discovered him and so when they found the baby Seg-El in his spaceship they decided to adopt him and gave him the name Sheldon Sampson and they raised Sheldon as their own and teaching him their values.
Sheldon Sampson grew up happily thanks to his good parents and he had great friends but eventually Chester and Betty told Sheldon the truth of his origins when he was old enough however Sheldon had always know that he was different from everyone else because of his incredible powers which he secretly used to help his family on the farm but only there as they told Sheldon that other people may be afraid of him because of his powers or the fact that he was a alien.
However in 1939 the Second Great World War started and Sheldon choose to fight in the war using his super powers while wearing Kryptonian armor with the symbol for the House El on the chest which looked like a 'S' inside a diamond shape which caused people began to call him 'Superman' and use him as their symbol of peace for those dark times.
During the war he met other people who also possesses super powers similar to his own like Princess Diana of Themyscria who was known as Wonder Woman and whom Sheldon fell in love with and married, Grace Kennedy who was known as Power Woman, George Hutchence who was known as Batman, Fitz Small who was known as The Flash, Richard Conrad who was known as Green Lantern, Namor who was the King of Atlantis and he is also known as the Sub-Mariner, Henry Heywood who was known as Sergeant Steel, Ten Knight who was known as Star-Man, and many other superheroes and together they became known to the world as 'The Union of Justice'.
Yes on this Earth I'm using the Superhero team name from Jupiter's Legacy The Union of Justice and gave this Earth version of Superman the Earth name of Sheldon Sampson which is the name of The Utopian as he's basically another copy of Superman like how the rest of the Union of Justice are copies of the Justice League
This world's Superman costume look like The Utopian's costume but with the Superman symbol on the chest
Grace Kennedy marries Sheldon Sampson 'The Utopian' and she is called Lady Liberty who is the Jupiter's Legacy version of Wonder Woman
George Hutchence is the name of Sky Fox who is the Jupiter's Legacy version of Batman
Fitz Small is the name of The Flare who is the Jupiter's Legacy version of The Flash
Richard Conrad is the name of Blue Bolt who is the Jupiter's Legacy version of Green Lantern
Yes I'm using Namor the Sub-Mariner from Marvel Comics as there isn't a version of Aquaman in Jupiter's Legacy