It might be to tie the game and anime universes more closely together. Since Red is a significant character in the games and Ash in the anime, making this connection in fanfiction can be a way to blend the two worlds. Also, it could be a way to explain Ash's seemingly innate ability to bond with Pokemon, as Red is a very skilled trainer. If he were Ash's father, those skills could be hereditary.
One reason could be to create a more complex family history for Ash. It gives his character more depth.
In fanfiction, making Pokemon Red Ash's father can be a means of exploring different storylines. For instance, it could lead to stories about Ash learning about his father's past adventures and using that knowledge to become a better trainer. It also allows for the exploration of how Ash might inherit Red's Pokemon if he were his father. Additionally, it can be a way to introduce new characters related to Red into Ash's story, like his grandparents or other relatives, which can open up a whole new set of plot possibilities.
In some fanfictions, Pokemon Red can be depicted as Ash's father. Fanfiction often takes creative liberties with established characters and relationships. Writers might create this connection to add a new layer of depth to Ash's backstory or to explore how certain Pokemon training traditions could be passed down within a family.
If Red was Ash's father in a Pokemon fanfic, Ash might start with a Pikachu like in the original series, but it could be a special Pikachu that Red had some connection to. Maybe it was a Pikachu that Red had trained briefly or had a unique bond with.
In the 'pokemon red is ash's father' fanfiction, one main plot point could be Red's past adventures and how they set the stage for Ash's future. Maybe Red left behind some unfulfilled tasks or prophecies that Ash is unknowingly meant to complete. Another plot point might be the reactions of the other Pokémon characters when this relationship is revealed. And there could be a plot about Ash struggling to come to terms with this new - found knowledge about his father while still continuing his journey to become a Pokémon master.
Betrayal could also stem from a misunderstanding. Maybe Ash or Cynthia accidentally offend someone without realizing it. For example, they might unknowingly step on a trainer's dreams or beliefs. And that trainer, feeling deeply hurt, decides to betray them. Or it could be that a Pokemon they both have a connection with has a different loyalty that they were not aware of, which leads to the Pokemon causing their betrayal.
Well, in the 'pokemon red is ash's father' fanfiction, the evidence might be quite tenuous. It could be something like Red's influence on Ash's journey in a very indirect way. Maybe the fanfic writer makes Red leave behind some sort of legacy or power that Ash unknowingly inherits. But this is all just speculation within the realm of fan - created stories and not based on the real Pokémon franchise.
He could be an ex - champion who had to give up his title for some noble reason. Now that he meets Ash, he wants to see his son reach the same heights.
If Red was Ash's father in a Pokemon fanfic, it would likely change the story in many ways. For one, Ash might have a natural aptitude for Pokemon battles from the start, as Red is a very skilled trainer. Also, he could inherit some of Red's Pokemon or have access to special training methods. Maybe Ash would be more confident and have a different attitude towards his journey.
There are indeed such fanfictions. This idea might stem from the similarities between Red and Ash in their love for Pokémon and their determination in training. In these fanfictions, the writers often create scenarios where Red passes on his knowledge or Pokémon to Ash, or there are family - related adventures that involve both of them.
Another theme is redemption. If the father figure has made mistakes in the past, like Giovanni perhaps, the fanfiction might focus on his journey to make up for those mistakes and be a proper father to Ash. This could involve him changing his ways and helping Ash in his Pokémon journey instead of causing trouble.
In Pokemon fanfiction, the claim that Sir Aaron is Ash's father is often a product of the creative minds of fans. Fanfiction allows for a lot of speculation and alternative storylines. There could be fanfictions where they base this on some kind of time - travel or reincarnation theory, or just a simple connection they make between the two characters' personalities or abilities. But the official Pokemon story has no connection between them, and these fan ideas are just for the enjoyment of those who like to explore different scenarios.