I offer this idea to anyone who wants to make something out of it.
In an alternate universe Jor-El has no son to send away to Earth and instead programs nanomachines to seek out a breeding pair of humans and alter their DNA, giving his race a chance to start again. Conveniently the first humans that come across this capsule of nanomachines are Johnathan and Martha Kent. They become this Earth's Superman and Superwoman. They may also have an adopted son, Clark, who has no powers.