She could have Katniss's dark hair and Peeta's blue eyes. Her features might be a blend of their strong and determined looks. Maybe she has Katniss's high cheekbones and Peeta's soft - looking lips.
Perhaps she has a petite frame like Katniss, but with Peeta's broad shoulders in a more delicate form. Her hair could be long and wavy like Katniss's, but with a lighter shade, a mix of Katniss's dark and Peeta's fairer hair color. And her eyes, while blue like Peeta's, could have a glint of Katniss's fierceness in them.
Peeta would probably be very nurturing. He has a kind heart, so he'd be great at taking care of the baby's basic needs like feeding and changing diapers. Katniss, on the other hand, might be a bit more cautious. She's used to being in survival mode, so she'd be constantly on the lookout for any potential threats to the baby.
They would become more united as they have a new life to protect. Their focus would shift from just each other to their baby, and they would work together even more closely.
Their lives would change in terms of their time management. With a second baby, they would have less time for themselves and more time dedicated to taking care of the child. They might also have to adjust their living space to accommodate the new family member.
Maybe the story could focus on the challenges they face as new parents. Katniss might struggle with being over - protective, given the dangerous world they live in. Peeta, on the other hand, is more laid - back. Their baby girl could have some special abilities, like being able to communicate with animals like Katniss, which brings both excitement and fear as they try to keep her safe from those who might want to use her for their own gains.
The baby might grow up to be like Katniss, strong and independent. Having seen his/her mother's courage in the Hunger Games, the baby could inherit that fearless spirit and be a great defender of their community.
The baby could be a unifying force. Just as Katniss was a symbol during the rebellion, the baby could symbolize a new beginning. People would see it as a sign of a better future, and different districts might come together to protect and support it.
One common theme is family. Since it's about them having a baby, it often focuses on how they build a family unit. How they protect and care for their child.
One possible scenario in the fanfiction could be that Katniss and Peeta's baby becomes a symbol of hope in the districts. The baby might grow up with unique skills inherited from its parents. For example, having Katniss's archery skills in a more developed way in the future. It could also be that the baby's existence is a threat to the Capitol, so they have to keep it hidden and protected at all costs.
Survival in a new context is also a theme. They had to survive the Hunger Games, and now they have to survive the challenges of raising a child in their post - Games world. For instance, protecting the baby from any threats that might still lurk in their society.
Their relationship might become even stronger. With a baby, they have a new bond that ties them together more tightly. They would rely on each other more for support in raising the child.