Well, a common trope is the 'protective parents' one. Even if they're not around, their influence still protects Roy and Edward in some way. It could be through a charm or a spell they left behind. Also, the 'tragic love' trope for their parents can be used. Maybe their parents had a love that was doomed from the start, and this backstory adds depth to Roy and Edward's characters. And sometimes, there's the 'parent as a mentor' trope, where through memories or some magical means, their parents guide Roy and Edward in their growth.
One popular trope is the 'lost past' trope. Maybe their parents had a secret past that gets uncovered in the fanfiction. For example, they could have been part of a secret organization. Another is the 'legacy' trope, where Roy and Edward discover something important about their parents that has a big impact on their own lives, like a hidden power or a mission they left unfinished. And of course, there's the 'family secrets' trope, which often involves things like hidden relationships or events that were never spoken of before.
Some popular tropes include the 'estranged parents' trope. Maybe there was a big fight or misunderstanding between Roy and Edward's parents before they passed away or disappeared. This can create a lot of drama and tension in the fanfiction. Then there's the 'redemption' trope. If their parents made some mistakes in the past, the fanfiction could explore how they try to make up for it, even from beyond the grave. Also, the 'parallel lives' trope, where Roy and Edward start to live out similar situations to what their parents went through.
Often, their father might be depicted as a strong and stoic figure. He could be a great leader type, someone who was respected in his community or among his peers. Their mother, on the other hand, could be seen as a nurturing and kind - hearted person. Maybe she was the one who taught Roy and Edward important values when they were young, like compassion and loyalty.
A really interesting plot twist could be that Roy and Riza are from a different time or dimension and they end up in Edward's world and become his parents. This could introduce all kinds of crazy elements into the story, like different alchemical rules or cultural differences. Edward would have to deal with the fact that his parents are so different from everyone else and that they might be in danger because of their origin.
One popular Roy and Edward fanfiction might be those that explore their relationship in different AU (alternate universe) settings. For example, in a modern AU, they could be college students dealing with normal life problems while also having their unique bond. Another type could be adventure - themed, where they go on a quest together, relying on each other's skills, like Roy's alchemy knowledge and Edward's combat abilities.
One popular trope is the 'soulmate' concept. In these fanfictions, Bella and Edward's connection is often portrayed as a fated, unbreakable bond that goes beyond the normal vampire - human relationship in the Twilight series. For example, they might be able to sense each other's emotions from great distances.
Roy and Riza would probably have a very hands - on approach to Edward's growth as an alchemist. Roy, with his knowledge of alchemy and military tactics, would teach Edward how to use alchemy in combat situations. Riza, on the other hand, would instill a sense of discipline and respect for the rules of alchemy. Their combined influence would make Edward a well - rounded alchemist. He would not only be skilled in performing transmutations but also understand the ethical and practical implications of his actions. This would help him grow not just in terms of his alchemical abilities but also as a person who uses alchemy responsibly.
One popular trope is the over -protective jealousy. Edward, being over -protective of Bella, gets jealous easily when he thinks she might be in danger from other male characters. It shows his deep -seated fear of losing her. Also, there's the 'green -eyed monster' trope where Bella's human insecurities surface as jealousy when she sees Edward's supernatural allure attracting others.
One possible fanfiction could be about Edward and Roy teaming up for a dangerous mission. Maybe they have to infiltrate an enemy stronghold where they discover a new type of alchemy that they've never seen before. Along the way, they start to understand each other better and respect the other's skills.
In many of these fanfictions, the 'discovery' trope is often used. It's about how they first find out about the pregnancy. It could be a shock, or there could be some signs that they initially misinterpret. And then there's the 'adaptation' trope. They have to adapt to the physical and emotional changes that come with the pregnancy, which is not easy given their vampire and werewolf natures.
Another reason is the depth of the 'Fullmetal Alchemist' universe itself. With its complex alchemy system, political intrigue, and moral dilemmas, there are so many elements that can be incorporated into fanfiction about Edward and Roy Mustang. Writers can take these elements and create unique stories that still feel like they belong to the same universe. For instance, they can explore how Edward's knowledge of alchemy would interact with Roy's plans for military reform, or how they would both deal with a new form of alchemy that has emerged.
One popular theme is friendship development. Many fanfictions focus on how Edward and Roy Mustang start off as distrustful of each other and gradually become friends. For example, stories might show them working on a project together and slowly realizing they have more in common than they thought. Another theme is power dynamics. Given Roy's position in the military and Edward's unique alchemical abilities, exploring who has more influence in different situations is quite common.