Perhaps the fanfiction could explore how their relationship evolves with the new addition. Prince Caspian, being a leader, would need to balance his duties with being a father, and Susan would have to use her wisdom to protect their child. The baby could become a symbol of hope for the future of Narnia, uniting different factions.
Well, in the fanfiction, the baby might be the key to a new era in Narnia. It could be that there are prophecies surrounding the baby's birth. Prince Caspian and Susan would have to raise the child in secrecy at first, fearing for its safety. As the baby grows, it starts to show signs of great power, and they must then decide how to present the child to the world of Narnia and deal with the various reactions.
One possibility could be that the story focuses on how they adjust to parenthood in the magical world. They might face challenges from those who oppose their union or from the powers that be in Narnia. The baby could also have some special powers or a great destiny.
A plot could involve Caspian being cursed and Susan being the only one who can break it. She has to go on a quest to find a magical object. Caspian, in his cursed state, can't directly help but his spirit encourages her. Along the way, Susan discovers her own hidden powers and in the end, she breaks the curse and they confess their love for each other.
A possible plot is that Susan discovers she is pregnant during a time of unrest in Narnia. Caspian is worried about how to protect her and the unborn child. They decide to go into hiding for a while in a secret part of Narnia. There, they live a simple life, and Caspian learns to be more self - sufficient, like fishing and hunting for food. As the pregnancy progresses, they form a deeper bond. Eventually, they return to the kingdom when things have calmed down, and they are welcomed with open arms as they await the birth of their child.
Another theme could be the integration of Susan's human world values and Caspian's Narnian ways when it comes to parenting. This can lead to interesting cultural clashes and reconciliations. And of course, the theme of love is always present, not just the love between Susan and Caspian but also their love for their baby and how it shapes their actions and decisions in the story.
One idea could be that Susan returns to Narnia during a time of great peril, and she and Prince Caspian have to team up to defeat a new, powerful enemy. They might discover hidden powers within themselves along the way.
One idea could be that Susan returns to Narnia in a time of great need, and she and Prince Caspian have to work together to defeat a new, powerful enemy. Maybe they discover an ancient magic that only they can unlock through their combined efforts.
You can try fanfiction websites like Archive of Our Own. It has a large collection of fanfictions, and there's a good chance you'll find some Caspian and Susan baby fanfiction there.
One popular Caspian and Susan baby fanfiction might be the one where they raise their baby in a magical forest. It shows their love for each other and how they pass on their values to the child.
It could be a jealous sorcerer who was once in line for the throne of Narnia. Now that Prince Caspian has married Susan, he sees his chance of power slipping away. So he tries to create chaos and turn the Narnian people against the new couple.
One possible plot could be that they face challenges in Narnia while Susan is pregnant. Maybe there are threats to the kingdom that they have to deal with together, all while preparing for the arrival of their child. Caspian might be extra protective of Susan, and they could rely on the help of their friends in Narnia.
The story could have a big impact on the magic in Narnia. Maybe the baby has a unique connection to the magic of the land, and its presence could either strengthen or disrupt the existing magical balance. Also, the idea of a new heir could inspire new quests and adventures, as various characters in Narnia would want to be part of the baby's life and future.