Perhaps the fanfiction could focus on the family dynamic. The twins could be very different in personality, causing some interesting family situations. One twin might be more adventurous like Percy, always getting into trouble, while the other is more studious like Annabeth. Percy and Annabeth would have to balance their roles as parents, dealing with the normal family issues as well as the challenges of raising demigod children.
The plot might revolve around the discovery of the twins' special destinies. Since they are the children of two very powerful demigods, they could be key to solving a major problem in the world of Greek mythology. For example, they might be the only ones who can stop an ancient evil from rising again. Percy and Annabeth would then have to guide their children on this dangerous quest.
One possibility could be that the twins inherit different powers from their parents. Maybe one has Percy's water - controlling abilities and the other has Annabeth's strategic mind and combat skills. They could grow up facing new threats in the demigod world, with Percy and Annabeth having to protect them while also teaching them how to use their powers.
They would likely raise them with a strong sense of honor and courage. Percy would teach them about the power of the sea and how to use it for good. Annabeth would instill in them a love for knowledge and strategy. They would also train their twins in combat skills to protect themselves in the dangerous world of demigods.
One possible plot could be about their journey of preparing for the baby. Percy might be worried about protecting his family from the various threats in their world, while Annabeth could be focused on creating a stable home environment. They'd also have to deal with the reactions of their friends like Grover and the other demigods.
One possible plot could be Percy and Annabeth adjusting to college life while also dealing with new mythological threats. Maybe they have to take on a monster that is hiding in the college library, using their demigod skills and the knowledge they gain from their classes.
One possibility could be that they are in a school setting where they have to wear uniforms. Percy might constantly be getting in trouble for not following the uniform code properly, like having his tie askew or his shirt untucked. Annabeth, being more organized, tries to help him out. This could lead to some comical moments as well as deeper conversations about fitting in and following rules.
Well, perhaps Percy takes Annabeth on a quest to a special location, like an ancient Greek ruin they've always wanted to explore. During this adventure, he finds the perfect moment when they're alone and surrounded by the beauty of the place to pop the question.
It could be a beach day scenario. Maybe they are having a day off from their adventures and just relaxing on the beach in their bikinis and swim trunks, enjoying the sun and having some light - hearted conversations.
One possible plot could be their daily adventures in a new city. They might face challenges like dealing with strange neighbors or finding new jobs. Maybe they also have to hide their demigod powers from the normal humans around them.
The fanfiction could also focus on the relationship between Annabeth and Percy during this time. They might have disagreements on how to handle the situation. For instance, Percy might want to keep Annabeth safe at all costs and not let her go on any dangerous missions, while Annabeth feels that she needs to be involved to protect their child. This could lead to some tension between them, but in the end, they would work through it and become even closer as they anticipate the birth of their baby.
Perhaps in this fanfiction, a villain has somehow transferred Percy's power of hypnosis to himself and uses it on Annabeth to get information from her. Percy then has to race against time to break the hypnosis and save Annabeth, all while facing various challenges and obstacles set by the villain.
One possibility could be that they are banished due to a false accusation. Maybe someone in the camp frames them for a serious crime they didn't commit, like stealing a powerful magical artifact. So, they are forced to leave and then have to prove their innocence while on the run from those who banished them.