Probably the children of various legendaries such as Articuno, Zapdos, and Moltres. They each might have distinct personalities based on the nature of their parent Pokemon. For instance, the child of Articuno could be calm and collected, while the child of Zapdos might be more impulsive. And there could also be a trainer or two who befriend the children and help them on their journey.
Obviously, Ash is one of the main characters. Since it's about him being a legendary Pokemon in this fanfiction, he's central to the story.
Obviously, Ash is one of the main characters. He's the protagonist who has a passion for pokemon and is always eager to become a pokemon master. And the legendary pokemon he encounters or befriends would also be important characters. For instance, if it's Lugia, Lugia would play a major role in the story as it's a very powerful and mysterious pokemon.
Obviously, Ash is one of the main characters. He is the trainer who gets the legendary starter. And of course, the legendary starter itself is also a main character. It has its own personality and abilities that play a big role in the story.
The villains in the fanfiction can also be considered main characters in a sense. They might be after the power of the legendary Pokemon. There could be a team of bad guys who are trying to capture and control a Groudon or a Kyogre to cause chaos in the Pokemon world, and Ash has to stop them. Their actions and plans create the conflict that Ash has to overcome in the story.
Often, the antagonists in these fanfictions are popular. Imagine an evil team that wants to capture the legendary starter for their own dark purposes. Their leaders, with their devious plans and menacing auras, can draw a lot of attention. Another popular character could be an old sage - like figure who has knowledge about the legendary starters and can offer guidance to the main characters.
Obviously, the Legendary Pokemon would be a main character. It could be a Pokemon like Mewtwo, who is often depicted as having a complex personality. It might start off as a mysterious and powerful entity that Ash has to befriend or battle against.
Articuno, Zapdos, and Moltres are quite common. Their elemental powers and the mystery surrounding them make for great fanfiction material. Ash might encounter them during his travels and have to either help them or face off against them in some way.
One of the Legendary Pokemon could be Giratina. Despite its somewhat dark and otherworldly nature, Giratina might be intrigued by Ash's light - heartedness and his ability to make friends with all kinds of Pokemon. Dialga and Palkia could also be part of the harem. Dialga, with its control over time, might see Ash as an important factor in the future of the Pokemon world. Palkia, in charge of space, could be interested in how Ash navigates different regions and spaces in his journey. And don't forget about Ho - Oh. Ho - Oh is a symbol of hope and might see Ash as a bringer of hope in the Pokemon world, thus joining his harem.
Arceus is quite popular. Given that it's considered the creator of the Pokemon universe in the official lore, it often has a significant role in fanfictions. Mewtwo is also very common. Its powerful psychic abilities and complex backstory make it a favorite for fanfic writers to explore. Another popular one is Lugia. With its majestic appearance and its connection to the sea, it's often a central figure in many stories.
One interesting storyline could be the children having to discover and control their latent powers inherited from the legendary Pokemon. They might face challenges like being hunted by those who want to use their powers for evil.