here's some proposals, ive had these ideas for a while now and if u want i can go more in-depth with the explanations
superman-after krypton is conquered by darkseid one ship of refugees wanders the universe looking for a new home, an explosion on the ship forces jor-el and lara to jettison their twelve year old son kal-el to save him from certain death. he lands three years later in kansas where hes taken in by the kents.
batman-his father an abusive, womanizing, alcoholic and his mother a pill-popper in denial, Bruce Wayne had a very sad childhood. When Thomas went too far and severely beat Martha, Bruce out of sheer terror killed his father with the man's own gun. Martha, still under the influence of pain-killers took the gun and shot herself. To keep Bruce safe, Alfred the family butler, took the fall and was sentenced to a ridiculous term due to a corrupt judge who had been Thomas' friend. Taken in by Dr. Leslie Tompkins, Bruce swore he would bring justice to the corrupt people like the judge and his father.
Wonder Woman-Themyscira, a paradise of ancient Greek culture, nestled deep in the Amazon jungle, is home to a civilization dominated by women where men are enslaved and used for labor and breeding. when a u.s. military helicopter crashes near the city, Princess Diana, eldest daughter of Empress Hyppolota, leads an assault on the downed soldiers. only one soldier survives, Capt. Steven Trevor and he is taken to the breeding pens. impressed with his fighting spirit, Diana falls in love with him. before the two can escape the city, Diana's treacherous sister, Donna reveals the two and Trevor is executed. As punishment, Diana is exiled from Themyscira and forced to integrate into man's world, acting as a spy for the Themyscirans. She kills and takes the identity of a young secretary in Metropolis, Lois Lane.
more to come