Fanfictions that focus on their family relationships could also be great. Maybe stories about how they interact with their Kryptonian heritage within the context of the modern world. They could be exploring old Kryptonian traditions while also dealing with the challenges of living on Earth, which can be a really interesting mix of the old and the new for them.
One popular story might be about their adventures together in an alternate universe where they have to team up against a powerful new villain. In this fanfiction, their powers combine in unique ways to defeat the foe.
You can try some well - known fanfiction websites like Archive of Our Own (AO3). It has a large collection of fan - created stories, and you might be able to find some Superboy and Supergirl fanfictions there. Just make sure to use the search function properly.
People write it because they like to explore different relationship dynamics. Superboy and Supergirl are both powerful characters, and seeing them in a romantic relationship can be exciting.
There could be a fanfiction where Superboy and Supergirl are in an alternate universe. In this universe, they are not related as in the traditional stories. They meet at a superhero gathering and the kiss happens spontaneously, leading to a whole new relationship dynamic.
Lex Luthor could be a great antagonist. He could be jealous of their combined power and try to create a device that can split them up or weaken their powers. He might also try to turn the public against them by framing them for crimes they didn't commit.
One idea could be that they team up to face a new and powerful villain from another dimension. This villain has the ability to nullify their powers temporarily, so they have to rely on their wits and non - superhuman skills. Another plot could be that they discover a long - lost Kryptonian artifact that holds the key to saving Earth from a natural disaster, but they have to solve a series of complex puzzles to unlock its power. Or perhaps they meet in a situation where they initially don't recognize each other as Superboy and Supergirl, and there's some humorous misunderstandings before they figure it out.
One interesting storyline could be Superboy and Supergirl teaming up to face a new and powerful villain that the Justice League has overlooked. They might discover a hidden threat in Smallville that has ties to Krypton's past.
Often, Superboy is really well - written. Writers can explore his struggle with his identity, being a clone. He has the power of Superman but also his own unique perspective, which makes for great character exploration in fanfiction.
Supergirl has super strength which allows her to lift extremely heavy objects. She also has heat vision that can be used as a weapon. And of course, she can fly. Wonder Woman, on the other hand, has super strength as well, but she has unique weapons like the Lasso of Truth which can force people to tell the truth, and her indestructible bracelets which can deflect bullets.