One common theme could be the challenges of new parenthood. Like how Eli and Clare adjust to having a baby, dealing with sleepless nights and all the new responsibilities.
In the fanfiction, a big challenge could be their inexperience. Eli and Clare are new to parenting and they might make mistakes. For example, they could be confused about how to soothe a crying baby. There could also be family pressure. Maybe their families have different ideas about how they should raise the baby, which can cause arguments between them.
In the fanfiction, Eli and Clare might be in a big city. They discover they're having a baby quite unexpectedly. At first, they're a bit scared but quickly become excited. Clare has to deal with her work while being pregnant, but her colleagues are very supportive. Eli takes on extra jobs to save money for the baby. They go to parenting classes together and learn a lot. When the baby arrives, it fills their lives with so much love and they become a stronger couple because of it.
I'm not sure specifically which 'eli and clare baby fanfiction' is good. You could try searching on fanfiction platforms like Archive of Our Own. They usually have a wide variety of fanfictions, and you might be able to find some great ones about Eli and Clare having a baby there.
Their relationship would likely become more serious. They'd have to rely on each other more for emotional support. There would be less time for just having fun and more time for discussing practical matters like doctor's appointments and baby - proofing their living space.
One good story could be 'Clare and Eli's New Beginning'. It focuses on how they adapt to life with a new baby, showing their struggles and joys. It beautifully portrays their relationship growth in this new phase.
One common theme is love and friendship. Since Clare and Eli are often friends before becoming romantically involved, their bond is explored deeply. Another theme is growth. Their characters develop as they face different challenges together in the fanfictions.
First, start with a clear plot in mind. Decide if you want it to be a story about their struggles with parenting, or more about the joys. For example, you could start with Clare finding out she's pregnant.
One great Eli and Clare fanfiction could be about their post - high - school adventures. Maybe they travel the world together, exploring different cultures and strengthening their relationship. Another could be a story where they face a big challenge in their relationship but manage to overcome it through communication and understanding.
Another place to find Eli and Clare fanfiction is FanFiction.net. It's been around for a long time and has a vast amount of fan - written stories. Just use the search function and type in 'Eli and Clare' and you'll get a list of relevant stories. Some Tumblr blogs might also feature or recommend Eli and Clare fanfiction.