Wait wait pls tell me more :’(
well the story has been retold twice or thrice, but mon-el is far more connected to superman, and really had nothing to do with supergirl other than he arrived before her, but after superman. clark was still a kid when another alien crash landed in kansas and had amnesia of all things. tiny clark just up and assumes its his big brother from space because, why the fuck not? clark names him mon-el because he landed on a monday and kids are bad at naming things. and then mon-el picks a human name ‘bob cobb’ because amnesiacs are bad at naming things. (mon-els public name was modernized to jonathan kent in recent versions and i strongly disagree with this choice. fucking stanning bob cobb for life ppl)
but later when bb clark starts to suspect mon-el isnt family/kryptonian he gives him a hunk of green painted led and calls it kryptonite to see how mon-el will react. this, because its the 1960s and plot logic is already running thin in comics, restores mon-els memories so he knows he is really a guy named lar gand from daxam, a krypton adjacent planet/race, who met jor-el like 5 seconds before the planet exploded and set sail for earth (???? dont look at me i diddnt write it) and also the lead is killing him because lead is daxamite kryptonite
really its all very stupid. but in a great way. mon-el is more or less beyond clarks powers to save so he puts mon into the phantom zone. because the clark kent basement is like a scifi movie set lol. i cant remember the comics exactly. but in the zone he can survive until there is a cure. which leads to the legion comics if im not mistaken. but i probs am so ill stop.
but thats the origin story of superman’s kinda sorta big brother figure. and its fun and dumb and silly and sweet and honestly, clark would have some harsh words for kara’s treatment from their kinda sorta realtive/brother/cousin/… phantom-zone-tenant. its weird. but not as bad as the cw made it ok