The Pokémon could play a role in their relationship growth. For example, if Ash and Serena have an argument, their Pokémon might nudge them towards each other to make up. Maybe Pikachu would give Ash a little shock when he's being stubborn, and Fennekin would snuggle up to Serena to cheer her up. And during special occasions like their anniversary, their Pokémon could participate in the celebration. For example, all of their Pokémon could put on a little show for them.
Their Pokémon could be like family members in their married life. For instance, Pikachu might sleep at the foot of their bed, just like a pet. The Pokémon could also help with daily tasks. For example, Serena's Fennekin could use its Fire - type moves to help with cooking. And Ash's Greninja could assist in fishing by using its speed and agility to catch fish in a nearby stream.
Pikachu would be super excited. It has been with Ash for so long and would see Misty as part of the family. It might play more with Misty's water - type Pokémon. Misty's Starmie could be very protective of the new family unit and use its psychic powers to help around the house sometimes.
Some of Ash's more competitive Pokémon, like Charizard, might be a bit protective at first. It might see Lillie as someone who could take Ash away from their adventures. But once it realizes how happy Ash is, it would warm up to the idea. Lillie's Pokémon that are more timid, like the Mareanie she has, might be a bit shy around all the new people and Pokémon at the wedding, but still be happy for their trainer.
Their Pokémon might be very protective. For example, Pikachu could stay closer to Serena all the time, sensing the new life. Some Pokémon might bring small items like berries or soft leaves, thinking it could be useful for Serena or the baby.
Pikachu would probably be very excited. It might jump around Ash, making little electric sparks of joy. Bulbasaur could bring Serena some fresh berries it finds in the forest as a sign of care. Eevee, if they have one, might curl up next to Serena's belly, as if protecting the unborn baby. Their Pokémon would sense the importance of this new development and do their best to be helpful and protective.
There are indeed. These fanfictions usually focus on the deepening of their relationship. For example, one story could be about Ash finally realizing his true feelings for Serena after all their adventures. Then, they get married in a beautiful ceremony attended by all their friends and Pokemon. It shows their love growing and evolving, which is very heartwarming.
When Ash presents Serena with a special gift during the wedding. It could be a flower crown made of the rarest flowers from all the regions they've visited together. Serena would be deeply touched because it shows how much Ash pays attention to their shared memories. Also, at the end of the ceremony, when they release a flock of Butterfree, just like when Ash released his first Butterfree. It symbolizes a new beginning for them, and this moment would be filled with a mix of nostalgia and excitement for their future together.
One possible plot could be that Ash finally realizes his true feelings for Serena after all their adventures together. They might return to a special place from their journey, like the Kalos region. Ash would plan a simple yet heartfelt proposal, perhaps involving their Pokémon. Then the wedding could be a grand affair with all their friends from different regions coming together. Their Pokémon would also play a part, like Pikachu being the ring - bearer.
Their relationship could develop with them learning more about each other's dreams. Ash might support Serena in her new cooking business that focuses on Pokemon - friendly foods. And Serena could encourage Ash to take part in more international Pokemon battles.
Ash's friends like Brock and Misty would be really happy for him. Brock might offer some relationship advice based on his own experiences. Misty would probably be a bit jealous at first but then be supportive. Lillie's family would be overjoyed. Her mother would be proud to see her daughter start a new life with Ash. And the Pokémon they have befriended would sense their happiness and be more affectionate towards them.
Well, it depends on what you consider 'good'. There are many fanfics out there. Some focus on the romance that led to their marriage, like how Serena finally confessed her love to Ash in a really dramatic way. Others might show how they handle challenges in their married life, like dealing with a rare and powerful Pokemon that threatens their peaceful existence in the Pokemon world.