There could be a new character, a rival to Ash's dad from his younger days when he was an active Pokemon trainer. This rival could reappear in the fanfiction, causing some trouble or adding some drama to the story.
Perhaps in this fanfiction, Ash's dad was once a great Pokemon trainer but had to give it up for some reason. Now, as a fan, he lives vicariously through Ash. He could be the one who inspired Ash to start his journey in the first place. He might have told Ash all those amazing stories about Pokemon when Ash was a little kid, which planted the seed for Ash's love for Pokemon.
Sure. In some fanfictions, the revelation of Giovanni as Ash's dad can lead to interesting plot twists. It might make Ash question his own identity and purpose. Also, it could potentially change the relationships between Ash and his Pokémon friends, as they may have to deal with the implications of Ash having such a powerful and often - villainous father.
Perhaps when Ash meets his dad, his dad is on a very important mission. Ash decides to join him, and during this journey, they face many challenges together. His dad could teach Ash some new battle strategies that are different from what he has learned before. They might also encounter some rare and powerful Pokémon that they have to work together to either capture or overcome. This meeting could be a turning point in Ash's Pokémon - training journey, making him more mature and experienced.
They could develop a mentor - student relationship. His dad, being more experienced, could teach Ash advanced Pokémon training techniques. Ash, in turn, could show his dad his unique way of bonding with Pokémon, which his dad might not have seen before, thus deepening their connection.
One possible story could be that the daughter, Ash's daughter, has been through some tough times at school. She comes home feeling really down, but her dad, Ash, is there for her. He makes her favorite meal and they sit down to talk. She looks at him with love in her eyes and says 'love you, dad'. And from that moment, their bond grows even stronger as they support each other through life's challenges.
Well, family drama is a big theme. There could be conflict between Ash and Giovanni at first, as Ash may not be able to accept a villain as his father. Also, the theme of power struggle can be present. Since Giovanni has a lot of power in the Pokémon world, Ash might have to deal with the expectations or threats that come with being his son. And secrecy is also a theme, as Giovanni may have kept this fact a secret for a long time.
The relationship can be developed through shared experiences. For example, they could go on a fishing trip together. While on the trip, they would have time to talk, share jokes, and Ash could pass on some of his wisdom to his daughter. This would strengthen their bond and she would likely say 'love you, dad' more often as they grow closer.
One possible scenario could be that Ash meets his dad in a Pokémon tournament. His dad could be a renowned trainer there. Ash would be shocked at first but then feel a sense of pride and excitement to compete against or with his father.