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 plot could be that they are competing in a friendly competition at Camp Half - Blood. It's like a series of challenges that test their skills, and along the way, they tease each other and have a great time. Their relationship is shown as a healthy, competitive one that is also full of respect.
Maybe they have a different taste in literature. They might prefer other types of stories and not be into the fanfiction genre, especially those related to Percy and Annabeth.
Percy might be a bit flustered and embarrassed. He's protective of his relationship with Annabeth, so having Magnus walk in might make him feel like their privacy has been invaded. He could quickly try to shield Annabeth or just look really shocked.
Their shared experiences play a big role. They've been through so much together, like countless battles and adventures. Percy has seen Annabeth in tough situations and he knows how strong she is, but also how vulnerable. So he feels the need to protect her. For instance, they might have had a close call in a previous adventure where Annabeth was nearly killed, and that memory makes Percy extra vigilant.
Their relationship is likely to be complex. They are friends and comrades who have fought side by side many times. So, there's a strong bond of loyalty between them.
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.
It is completely inappropriate. Fanfiction should be a platform for positive exploration of characters and their relationships. Percy and Annabeth's relationship in the original works is based on mutual respect, friendship, and a shared journey. Writing about 'angry sex' for them is a disrespect to the source material and its intended audience.
They can develop their relationship by having deep conversations. For example, sharing their fears and dreams about their future together. Maybe Percy tells Annabeth about his insecurities of not being a good enough husband sometimes, and Annabeth reassures him.
It could also be due to some sort of magic or mind - control. A powerful enemy might have cast a spell on Annabeth, forcing her to turn against Percy. In this case, it's not really her own will but the result of external manipulation.