Maybe Loki returns after being presumed dead. Thor is overjoyed at first, but then realizes Loki has some secrets he's been keeping. They have a tense but ultimately heartwarming conversation as they catch up on all that has happened.
In some fanfictions, Loki and Thor reunite in the middle of a battle. Loki has changed sides and is now fighting for the good. Thor is initially shocked but quickly accepts Loki's help. Together they defeat the common enemy and then have a long - awaited brotherly moment, reminiscing about their childhood and mending their relationship.
Loki might develop by becoming more honest with Thor. For example, he could finally admit his true feelings and intentions from past events. This would be a big step in his character growth.
In some fanfictions, they might reunite during a big crisis that affects the entire world. They are forced to put aside their differences and come together. Tony uses his intelligence to figure out a plan, and Steve, with his leadership and combat skills, leads the execution. Their reunion becomes a symbol of hope for everyone around them.
One interesting Young Loki and Thor fanfiction could be about their adventures in Asgard as kids. Maybe they get into trouble while exploring a forbidden part of the realm.
One interesting story could be about Thor and Loki having to team up against a new, powerful enemy that neither of them can face alone. This forces them to put aside their differences and use their combined powers and wits to save Asgard.
There's 'Thor's Redemption in Loki's Arms'. In this story, Thor realizes his true feelings for Loki after a series of events that nearly tear Asgard apart. It's a tale full of emotion and character development.
One plot idea could be Thor and Loki as younglings getting into mischief in Asgard's forbidden areas. Maybe they accidentally unleash a minor magical creature that causes chaos in the palace. Another could be a story where they compete in a friendly, yet intense, training tournament to prove who is the better warrior at a young age. And they could also go on a secret adventure outside of Asgard, defying Odin's rules, to explore a rumored enchanted forest.
One example could be a story where Loki's intersex nature adds a unique layer to his relationship with Thor. Maybe in the fanfic, Thor is initially confused but then becomes very accepting and protective of Loki. It could explore how Loki deals with his own identity in the context of Asgardian society, which might be less understanding compared to modern Earth concepts.
Another plot could be a what - if scenario. What if Loki didn't fall into the abyss in The Dark World? He could have used his trickery to manipulate the dark elves in a different way. He might pretend to side with them at first to gain their trust and then double - cross them to save Thor and Asgard. This would show his complex nature and his loyalty to his home, in his own twisted way.
One possible plotline could be Loki initially being angry and resentful towards Thor for hurting him. But as the story progresses, Thor's guilt drives him to make amends in a big way, like going on a dangerous quest to find a rare healing item for Loki. This could lead to a deeper understanding between them and strengthen their bond in the end.
One plot idea could be Thor becoming overly possessive of Loki after Loki gets too much attention from other Asgardians. Thor starts to isolate Loki, thinking it's for his own good. Another could be in a situation where Loki is injured, and Thor's yandere side emerges as he refuses to let anyone but himself tend to Loki. A third idea is that Thor, in his yandere state, tries to make Loki dependent on him by controlling all aspects of Loki's life in the name of protecting him.