In a fanfiction, Percy could become Annabeth's father in a magical realm where the rules of family and time are distorted. Maybe a powerful god or goddess messes with their destinies. Percy would then have to navigate the new relationship while still dealing with his own heroic duties. He might struggle to balance protecting her as a father and respecting her as an independent demigod who is used to taking care of herself.
Their relationship would likely become even deeper. They would be partners not only in their heroic adventures but also in parenting. They would have to support each other in raising their child, like Annabeth helping Percy understand their child's academic needs while Percy might be better at teaching combat skills. They would also have to make decisions together about their child's future, whether it's about staying at Camp Half - Blood or trying to live a more normal life in the mortal world.
The fanfiction might explore how Percy's relationship with other characters changes. For instance, he may have to face the judgment of Athena, Annabeth's mother, as he takes on the role of father. Athena could be skeptical or even hostile at first, but over time, Percy could prove himself worthy. Also, Percy would have to interact differently with his own friends and family, like his mother Sally, who might now be a grandmother - like figure to Annabeth.
Perhaps Annabeth's dad has some old - fashioned ideas. He might believe that Percy doesn't have the right qualities to be with his daughter. He could also be jealous in a way. Percy is an important person in Annabeth's life and her dad might feel left out or that Percy is taking his place in a sense.
It could be for the greater good as she perceives it. Annabeth might think that by betraying Percy, she can save more people or prevent a greater disaster. However, her perception might be wrong, and she realizes it too late after the betrayal has already occurred.
Well, they would probably communicate better. In Tartarus, they had to rely on clear communication to survive. So, back in the normal world, this would carry over. They'd be more open about their feelings, fears, and plans, which would strengthen their relationship in a more emotional way.
She might focus on her studies more. Since Annabeth is really into knowledge, she could pour all her energy into her schoolwork, like spending extra hours in the library or on research projects.
Annabeth could also try to solve the problem that's making Percy cry. If it's related to a quest or a danger, she'll start thinking of ways to fix it. In some fanfictions, she might say 'Don't worry, we'll figure this out together.' and then start making a plan.
They might become more protective. Since they are dreaming of having a daughter, they would start to think about all the potential dangers she could face. Their relationship could grow deeper as they bond over their shared hopes and fears for their future child.