Three sole survivors, one set from the asteroid belt between Mars-One and Jupiter-One, and the others from Neptune-Two. The two trios seek a new world, Earths One and Two, that they can make habitable to live on. Only one member of each triad of terror survive, once eggs turned into powerful aliens known as Xum and Egon.
Xum creates two aliases, as the super-powered Replikon and the humanoid Andre, so as to study humanity and his new world with the intent to terraform it into a new home for his children. In the interim, he encounters Green Lantern, Green Arrow and Black Canary on a couple of occasions and despite a curious romance with Carol Ferris, is bent on eradicating humanity. Instead, he is once more exiled back to the asteroid belt with his unborn eggs until another Lantern, John Stewart, arrives to assist Replikon by creating an atmosphere for the eggs to be born into.
Egon isn't a parent, but rather the child of a pair that die upon arriving on Earth. Himself hatched from an egg and quickly raised by Noel Ratchford, a jealous suitor of Sheila Sanders, the being is sent to attack the city in the name of Carter Hall... Sheila's boyfriend. In Carter's alias as the Hawkman, the winged warrior quickly dispatches the creature, ending its reign of terror and its misguided life as well.