Supergirl and Superboy are both long-time members of the Legion.  It is upon the memory and the Legend of Superboy that the Legion is built.

There is a close kinship between Kara, Kal-El and Mon-El.  This relationship is to be spotlighted.  Superboy and Mon-El are like brothers, and the two most powerful members of the team.  The three “Kryptonians” (tho’ Mon-El is really a Daxamite) are an inner trio—the power trio—within the team, just like Lightning Lad, Saturn Girl and Cosmic Boy are the leadership trio.

Supergirl has a relationship with Brainiac 5, the super-intelligent 12th level thinker.  He appreciates her own quick intelligence.

Supergirl is a universal legend from the 20th century come to visit three hundred years in the future.  She knows the man Superboy will become.

Superboy was born from a family of the Kryptonian elite, but raised a small-town Kansas son, all-American, as Clark Kent.  This is clear in the bright, pure character of Superboy.

Supergirl was raised on a surviving chink of Krypton—Argo City, sealed off from the vacuum of space, whose people lived by knowledge rediscovered from the ancients by Kara’s father, Zor-El.  She was one of a very few children, the first Kryptonians born by live birth in centuries.  Supergirl had come to Earth as a teenager.  She has a zeal for righteousness.

Mon-El also came to 20th century Earth as a teenager.  He arrived completely amnesiac except for his name—Mon-El.  Mon-El was discovered by Superboy, taking him to actually be his brother.  It turned out, however, that the radiation of lead was almost instantly lethal to him in sufficient doses.  He chose self-imposed exile in the Phantom Zone for one thousand years, until a cure could be found.

The shadowy realms of the purgatorial Phantom Zone were discovered by Superboy’s father the scientist priest Jor-El, who had met the young Daxamite.  Mon-El lived here in this phantasmic “Sheol” for one thousand years, until he was delivered by the Legion.  Thus is Mon-El the dark and silent brooding “older brother” to the Kryptonians.

All three of them are “orphaned” time travelers, born under a red sun and physiologically changed by a voyage through space and time, all arriving on the same planet—Earth—within the same quarter century.  All bearing the surname “El.”

Kara treats both of them as brothers, treating Superboy with a special respect.  She works well with the melancholy Mon-El.

And during their visits with the Legion, Superboy and Supergirl fill their minds with the wonders of their future, enriching their lives as 20th century citizens.

The Legion are in the rather unique position of knowing the history, the birth dates, death dates and secrets of all three.  And Brainiac most of all.  This is why, during the story, Saturn Girl and Ultra Boy, come to him and ask, “Why, if you know Supergirl’s fate and her destiny in the scheme of things, do you make the logistical folly of romantic involvement with her?”

Brainiac replies, “To be close to her.  Because it makes her even more precious to me.  It is precisely because I understand the events of her life that I love her, and with my 12th level computer mind, I know I can guide her more safely through those inevitable waters.”
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