Another reason could be loyalty issues. For example, if one of them is suspected of being too friendly with the enemy or making a deal that the other doesn't approve of. In a complex world of fanfic - created politics and relationships, this can be a major cause for a fight.
One possible reason could be jealousy. Maybe they both have feelings for the same person in the fanfic. Another reason might be a difference in their approaches to a mission or a problem they are facing. For example, Alec might be more cautious while Jace is more impulsive.
They could just sit down and talk it out. Once they realize that they were both acting out of misunderstandings or emotions, they might simply apologize and go back to being friends.
It's hard to say. Alec is very strategic and has great archery skills. But Jace is extremely fast and a master with the sword. If it's a long - range fight, Alec might have the upper hand. But if it gets up close, Jace would probably win.
In the fanfic, it might be a fight that's more about pride and proving who is the better Shadowhunter. Alec has his own set of skills and Jace has his. They might get into an argument about who is more useful in a certain situation, and it turns into a full - blown fight. Alec might use his strategic mind and archery skills, while Jace uses his speed and swordsmanship.
Well, sacrifice is a theme that pops up often. They would do anything for each other, even put their own lives at risk. This is seen in 'The Ultimate Sacrifice' fanfic. Additionally, growth is a common theme. As they face different challenges, they grow as individuals and as a duo. Their relationship is always evolving in the fanfics, which makes it really interesting to read.
Another reason could be that Harry has other priorities in the fanfic. He may be more focused on solving a mystery, helping a friend, or achieving a personal goal that doesn't involve fighting. So, fighting is not on his agenda.
Well, some writers might do it to show the imperfections of the characters. In the original story, Jace and Clary's relationship seems quite idealized at times. By writing a scenario where Jace cheats, it could be a way to break that ideal and show that they are complex characters with flaws. Also, it could be a way to explore different relationship dynamics and how they could change over time. For example, how would it affect their friendship with other characters? How would they deal with the betrayal? There are many possible storylines that could stem from this one idea.
They could fight due to a prophecy. If there's a prophecy that involves one of them being the 'chosen one' and the others think they should be, it would create a lot of tension. For instance, if the prophecy says that only one of them can save the world from a certain doom. Percy, being the main character in many stories, might be assumed by the others to be the one, but Thalia and Nico may believe they have just as much right. Their struggle for that role could lead to a fight. And during the fight, they would use their unique abilities. Percy would call upon the water, Thalia would summon her lightning bolts, and Nico would raise the dead to fight on his behalf.
Another reason could be different loyalties. Thalia has her own group of friends and allies, and Percy has his. There could be a situation where their friends' actions or needs put them at odds with each other. For example, if Percy's friends get into trouble with something related to Thalia's friends' territory or interests, it could spark a fight.
One popular theme is loyalty. Since they are parabatai, their unwavering loyalty to each other is often explored. Another theme could be sacrifice. For example, they might be willing to sacrifice their own desires or safety for the other. And friendship is also a big theme. Their deep bond as parabatai and friends can be shown in different ways like how they support each other through tough times in the fanfic.