Well, if we're talking about a 'pepa and silvia first time fanfiction', it might be important to consider the context within which this 'first time' is set. Is it their first time meeting, first time working together, or something more romantic? Without reading it, it's hard to say for sure. But often, a good fanfiction in this case would build up tension and anticipation before getting to the 'first time' moment, whatever that may be.
There's also George, Peppa's little brother. He's cute and often follows Peppa around. Then there are Peppa's parents. Her dad is funny and her mom is very kind and takes care of the family.
One interesting Pepa and Silvia fanfiction could be about their adventures in a magical forest. Maybe they discover a hidden realm and have to solve puzzles to get out.
One common theme is love and support. Since Felix is always there for Pepa, many fanfictions explore how their love helps Pepa manage her emotions better.
There could be fanfictions that focus on their relationship during difficult times in the Encanto. Maybe a story where they support each other through a crisis in the family, like when the magic was fading. They would rely on their love and understanding of each other to get through it.
You can try fanfiction websites like Archive of Our Own (AO3). It has a large collection of fanfictions from various fandoms, and there's a good chance you'll find some great Pepa and Silvia fanfictions there.
One great Pepa and Felix fanfiction is 'The Sunny Days of Pepa and Felix' on FanFiction.net. It beautifully portrays their relationship and how they handle the challenges in their magical world.
One possible theme could be friendship. If it's their first time doing something together like going on an adventure, it might highlight the bond of friendship between them.