There could be. Check out various fanfiction communities. They often have filters or tags that can help you find the more family - appropriate stories about Eren and Historia in this situation. It may take some searching, but they do exist.
One idea could be the two of them preparing for the baby. Historia might be learning about different parenting styles, and Eren could be building a nursery. It could show their growth as individuals and as a couple.
Fanfiction about Eren and Levi kissing can be quite interesting. It might explore a different side of their relationship. Some fanfictions in this regard could be about a moment of emotional intensity between them, where the kiss represents a deep connection that goes beyond their usual interactions in the original story.
Mikasa and Eren don't kiss in the manga. The focus of their connection lies in different aspects of their shared experiences and the evolving plot rather than a romantic kiss.
Sure, Mikasa kisses Eren. This occurs during a crucial and emotional part of the story that has a big impact on their relationship and the plot as a whole.