May would probably look up to Ash even more. Since Ash has a lot of Pokemon - related knowledge and experience, as her'mom', he could pass on some unique skills and wisdom. Their relationship might also have some emotional depth added to it, like when May is feeling down, Ash would be there to comfort her like a mother would, which is different from their usual trainer - to - trainer relationship.
There would be a shift in power dynamics too. Ash as the'mom' would have more authority over May. He would be able to make decisions for her in certain situations, like which Pokemon training camps she should attend. However, at the same time, he would also be nurturing her independence, teaching her how to make good decisions on her own as she grows up in the world of Pokemon.
Ash and May's relationship would deepen in many ways. With a baby on the way, they would start seeing each other in a new light. Ash, who was always adventurous, would now also think about the safety and well - being of his family. May would find Ash more reliable and loving. They would have to work together to create a stable home environment for the baby. For example, they might argue a bit about which Pokémon should be around the baby when it's born, but through these discussions, their relationship would grow stronger.
Ash would initially be heartbroken. He has shared so many adventures with May, and this betrayal would shatter his trust. He might go off on his own for a while to think things through. When he comes back, he could be more determined than ever to prove himself without May. He might also be a bit more cautious when it comes to making new friends. His Pokémon would sense his distress and try to comfort him, but it would take a long time for him to fully get over May's betrayal.
It could be that in an alternate universe, Ash is born as a much older person and becomes May's mother in a more traditional sense. He might have different Pokemon knowledge and experiences which he passes on to May. He could be strict about some things like safety during Pokemon battles and lenient about others, like letting May choose her own first Pokemon even if it's not the most common or powerful choice.
Ash could get angry. He has a strong sense of justice, and he might feel that May has violated their friendship. He could challenge her, not in a violent way, but more in a way to get an explanation and to try to make her see the error of her ways. He would likely be determined to show her that what she did was wrong.
Their relationship with other Pokémon would likely change quite a bit. For Ash, his other Pokémon like Charizard might initially be a bit aloof towards Plusle and Minun. But as they see how useful Plusle and Minun can be in battles and how they contribute to the team spirit, they would warm up to them. For May, her Pokémon like Eevee could start to develop new strategies in battles with the addition of Plusle and Minun. Plusle and Minun's presence could also encourage Ash and May's other Pokémon to be more social, as they are very social Pokémon themselves. This could lead to more group activities among all of Ash and May's Pokémon, like playing games together or exploring new areas as a united group.
I haven't come across a fanfiction where Ash turns into May's mom myself. But given the creativity of fanfiction writers, it's entirely possible that someone has written such a story. It could potentially be part of a more complex plot within the Pokémon fanfiction universe, perhaps involving some sort of magic or strange experiment gone wrong that causes this transformation.
At first, they might be a bit cautious around each other. But as they spend more time together, they start to respect each other's skills. Ash would come to admire May's Contest skills and May would be in awe of Ash's battle prowess. They could become like a team, always having each other's backs, whether it's in a battle or a Contest.
Definitely their Pokémon friends. Pikachu, of course, would be there. May's Blaziken and Ash's Greninja would also be among the guests. Their human friends like Brock, Misty, and Dawn would surely come. And perhaps some of the Gym Leaders they've met during their travels would also attend, like Roxanne from Rustboro City.
Sure. There are fanfictions where they are just good friends and they help each other out in Pokemon battles or in exploring new regions. Their relationship can be shown as a strong bond based on mutual respect and support without any romantic or inappropriate content.
They would become more united and responsible. Their relationship would shift from just being friends or fellow trainers to co - parents. They would need to communicate more about the baby's needs, like what kind of Pokemon - related education to give the baby.