In every universe, there is a version of each individual somewhere... sometime... which corresponds to his myriad of counterparts elsewhere throughout the multiverse. And yet, in each incarnation, radical events can cause each twin to diverge from his dopplegangers in signficant ways. One of the most illustrative examples of this are the boy known by different names... Tommy Tomorrow, Sandy Hawkins, Jed Walker and Kamandi. How can we connect all these individuals together as one-in-the-same in essence if not in experience? This will take some time, and deep ponderance indeed, although the journey to the answer to this question will deepen our appreciation of how time and circumstances can mold a person in a variety of ways.
First we have to start out by considering the Sandman ofEarth-Two, Wesley Dodds, who had began his costumed career in 1940 in a business suit, fadora and gas mask before adopting a more colorfully clad spandex garment like his contemporaries in the Justice Society of America. At that point, he adopted the orphan known as Sandy Hawkins, and quickly assimilated him into the world of mystery men as his sidekick. This lad had a memorable career alongside his mentor before an accident with a n experimental silicon gun mutated him into a creature of silicon, for which he was kept asleep for decades before finally being reverted to his carbon-based self, unaged as a result.
On the parallel planet of Earth-One, scientist Garrett Sanford developed technology allowing one to peer into the "Dream Stream" which tied people through their dreams. In order to safe the life of the President of the United States, Doctor Sanford entered this dimension to awaken the politician from his dream-like coma. As a result, Sanford found he could only return to his native dimension for one hour at a time each day, and hence decided to adopt the alias of Sandman. Becoming a superhero like Dodds, Sanford soon acquired his own sidekick of a sort in the form of Jed Walker. However, this lad was not from Earth-One! How is this so?
Initially, Sanford was drawn into a conflict with the supervillain known as General Electric when tipped off by the dreams of young Jed, who had discovered one of the General's killer dolls. After defeating the computerized egomaniac, Sandman and Jed had a few more adventures, until on one occasion the Master of Dreams encountered the young Kamandi following a surreal conflict which Jed had with his mentor. Within the Dream Stream base of the Sandman, Sandman revealed to Kamandi that his exploits as Jed Walker happened "on another time, on another Earth". Previously, Supergirl of Earth-One traveled to the future when an orphan named Tommy had unknowingly saved the visiting Maid of Might's life. She returned the favor, saving the vessel that transported Tommy's future adoptive parents, thereby insuring that he would be raised by General Horatio Tomorrow. As a result, the lad would grow up to become the legendary Tommy Tomorrow of the Planeteers, the galaxy's greatest hero of that era.
Now during the Crisis on Infinite Earths, it was revealed that the Kamandi who met Sandman was an alternate universe version of Tommy Tomorrow, hailing from Earth-AD. As such, since Kamandi was of that Earth, and Tommy was of Earth-One, while their counterpart Sandy the Golden Boy resided on Earth-Two. Hence, Jed's tale existed on a third Earth... perhaps Earth-Three (given that Sanford explained to Kamandi of alternate Earths using the Flashs of Earths One and Two as well as Earth-Three's Johnny Quick). However, there then is presented the dilemma of General Electric's existence. Who is this, you ask?
General Electric was a former Japanese soldier who's shattered brain was repaired using cybernetic enhancements that gradually turned him into an evil, and manipulative, genius. His actions drew Jed and, by extension, Sandman to him... and years later the General returned to menace Wonder Woman of Earth-One. However, since the Dream Stream ties together all realities, being the conduit through which writer Gardner Fox of Earth-One began chronicling the adventures of the Flash of Earth-Two, so too it was Jed's mind that picked up on Electric's activities a universe away... even creating a realistic image of the mastermind's Werblink device. Crossing the dimensional divide with the lad through the Dream Stream, Sandman defeated the criminal on Earth-One while being guided by the homing senses of Jed on Earth-Three. The pair would reunite a few more times, this time in Jed's home universe that appeared hero-less, which further identifies it as being Earth-Three.
Both Tommy and Sandy were creative and courageous, with the Planeteer using an anti-gravity and ray guns versus his foes, while Sandy used his wirepoon and gas guns against his enemies. Kamandi likewise was very ingenious and intense in defending any innocents he came upon. While Jed didn't have the acumen of his twins, he nevertheless made up for his lack of flash but his imagination.
And, as Doctor Sanford explained, a key event can prevent one counterpart to be born perhaps centuries after his cosmic twin in a parallel universe. Such would explain the existence of the Legion of Super-Heroes' counterparts on Earth-Two, the All-Star Squadron who were born over a thousand years before their Earth-One dopplegangers.