SUPERMAN 166 (January 1964)--"The Fantastic Story of Superman's Sons" by Hamilton, Swan and Klein; r. SUPERMAN 222 [G-66] (December 1969 - January 1970); cover art by Swan and Klein:
On one imaginary day which may or may not ever occur, Kal-El becomes the proud father of fraternal twins: the raven-haired Jor-El II who has super-powers and the brown-haired Kal-El II who has no super-powers. Their mother is only shown in silhouette and is never identified by name.
Young Kal-El II feels like a loser compared to his powerful twin. His parents see this and Superman is at pains to support his powerless son. The father goes to the extreme of finding a planet, one where metal life has evolved, with two suns (purple and orange), which he deduces should give Kal-El II super-powers. However, when the boy is left there to exist on his own, without his family, he grows homesick. At Christmas, he views the family celebrations on Earth and yearns to be there.
In response to his signal, Superman comes to the far planet and takes Kal-El II back home again. Next the Man of Steel concocts a formula that gives the lad super-powers, but the invisibility side effect robs him of his sight. Powerless again, the brown-haired boy feels he is only a burden to everyone and decides to run away from home, but the Man of Tomorrow soon finds him.
In the end, the father decides to take both boys into the bottle city of Kandor where, despite their young age, they attend the university. Even without super-powers, Jor-El II is still the physically superior one, while Kal-El II is the intellectual reading many books. Hearing about the legend of Nightwing and Flamebird, the brothers revive the tradition, putting on the costumes of the crime-fighting duo to track the Mystery Raider. This thief has been looting old Kryptonian scientific materials. Studious Kal-El II has a theory but Jor-El II doesn't want to hear about it, being fixated on the present danger.
With the materials he's stolen, the Mystery Raider has built a reverse evolutionary ray that devolves creatures to their monstrous throwbacks. The Raider escapes to go on a crime spree outside the bottle, devolving contemporary beasts of Earth into their predecessors.
Kal-El II's investigations of Kryptonese texts leads him to believe the answer is in the past and he takes a Time Bubble through time and space to Krypton, where he meets his grandfather, Jor-El I, before his marriage to Lara Lor-Van. Kal-El II introduces himself as Kalel Kent. They encounter a biologist named Gann Artar who has developed a de-evolutionary ray, but the Science Council forbids anymore experiments with this induced atavism.
Visiting the House of El family crypt, Jor-El is puzzled by the resemblance of his ancestors to Kalel. Jor-El has a dog that will eventually father Krypto. Seeking revenge against the Science Council, Gann Artar uses the de-evolutionary ray to transform the dog into a monster from Krypton's past. Jor-El develops a gas that reverses the effects of the induced atavism, then Gann Artar is arrested and sentenced to the Phantom Zone.
Returning to the present and having found that Gann Artar has escaped from the Phantom Zone, Kal-El II confirms that he is the Mystery Raider. Meanwhile, Superman and Jor-El II have tracked the Raider to his base in the Wild Mountains only to be felled by Kryptonite. Immune to the green stuff, Kal-El II faces down Gann Artar and uses the Phantom Zone projector to return the rogue to that eerie realm.
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Happy Holidays!