I'm sorry, but I'm not familiar with the specific 'Jayaraj and Fenix' story. It could be a very specific or local story, or perhaps it's something that is not widely known without more context.
In the beginning, Naruto and Riser may not get along well due to their different personalities and upbringings. Naruto is more down - to - earth and values friendship and justice, while Riser is more prideful. But when they discover they are brothers, they are forced to interact. As they spend time together, they realize they have more in common than they thought. For example, they both have a strong sense of protectiveness towards their loved ones. This realization could lead to them gradually building a strong relationship. Naruto might even start to understand Riser's pride as a form of self - confidence, and Riser could come to admire Naruto's selfless nature.
One common theme is the clash of different worlds. For example, when Marcus Fenix crosses over into a different game or movie universe, there's always the struggle to adapt to new rules, cultures, and technologies. This can lead to some really interesting scenarios where he has to figure out how to use his skills in a completely new context.
One popular Marcus Fenix crossover fanfiction might be the one where he crosses over with the Halo universe. In it, Marcus brings his unique combat skills and leadership to new and unexpected situations within the Halo setting.
Love and romance are also quite common themes. The OC might be someone who catches Marcus's eye and they develop a romantic relationship over time. This often involves a lot of character development for both as they navigate their feelings in a world full of chaos. Additionally, the theme of redemption can be present. Maybe the OC has a troubled past and Marcus helps them find a new path, or vice versa.
A great fanfic idea could be that Rias and Riser are sent on a joint mission to the human world. They have to blend in as high school students. This would be a comical and interesting premise as they struggle to adapt to human life while also dealing with their own relationship. Rias might be more empathetic towards humans, while Riser could be more arrogant at first.
One possible fanfic could be about a friendly rivalry between Rias and Riser that turns into a mutual respect. For example, they could start competing in various magical challenges within the Highschool DxD universe. This would show their growth as characters and how they overcome their initial differences.
Love and relationships are also common. Writers often create stories around Riser's romantic interests or his friendships. For example, some fanfictions focus on his relationship with his arranged marriage partner and how they grow to understand each other.
One possible fanfic could be about Riser and Kuroka forming an unlikely alliance. Maybe they start off as enemies, but due to some common goal, like protecting the underworld from a new threat, they have to work together. Their interactions would be filled with tension at first, as Riser is quite prideful and Kuroka is independent. But as time goes on, they start to understand and respect each other more.
There could be a fanfiction where Marcus Fenix travels to Forks. He discovers the world of vampires and werewolves. Bella Swan is intrigued by his combat skills and they form an unlikely friendship. In this story, they might exchange their different survival skills, with Marcus teaching Bella about combat and Bella showing Marcus how to navigate the complex social hierarchies in Forks.