One plot idea could be that the kiss is a result of a dangerous situation they've just overcome together. Maybe they were in a life - threatening situation, and in the relief of surviving, they share a passionate kiss.
One idea could be exploring how Thomas and Brenda prepare for the baby. Maybe they have to deal with unexpected challenges like finding a safe place to live in their post - apocalyptic world. Another plot could be centered around their fears and hopes for the future of their child.
I'm not sure of specific 'Thomas and Brenda kiss fanfiction' titles offhand. But you can try searching on fanfiction websites like Archive of Our Own or FanFiction.net. They have a vast collection of fan - created stories, and you can use their search filters to look for ones that focus on this particular moment between Thomas and Brenda.
A really interesting 'Brenda and Thomas kiss fanfic' could explore a different world or universe. They could be characters in a fantasy realm, and their kiss could be a magical event. It might be that their kiss has the power to break a curse or bring about some great change in their fictional world.
Perhaps there could be a story where Thomas and Edward compete in a friendly race. Along the way, they both learn important lessons about sportsmanship and friendship. For example, when one of them has a minor accident, the other stops to help, realizing that winning isn't everything.
They could get lost in an old, abandoned part of the railway. Thomas might be a bit scared at first, but Percy stays calm. Together, they explore the area, find old railway artifacts, and then figure out a way to get back to their normal tracks. It would be a story of discovery and courage.
Perhaps there's a magical event that only Thomas and the lady human can solve together. They might have to use their combined skills and knowledge. Thomas could use his physical abilities like speed or strength, while the lady human could use her intelligence or some special power she has to defeat an evil force that threatens their world.
You could also focus on a side character's perspective. For instance, a friend of the main characters who has always secretly liked one of them. This character could try to interfere with the relationship in 'it started with a kiss' in the fanfiction, creating a lot of drama and tension in the story.
One idea could be a forbidden love story where a human falls in love with a succubus. The succubus is initially only interested in his energy but gradually develops real feelings. Another could be a story set in a magical academy where a succubus uses her kiss to gain an advantage in a competition, but then finds herself falling for one of her rivals.
One idea could be exploring a different backstory for the main characters. For example, what if the characters met in a completely different setting before the events of the original story? Another could be a 'what if' scenario where a character makes a different choice at a crucial moment in the story. Maybe a character decides to trust someone they originally didn't, which could lead to a whole new set of relationships and plot developments.
Another place to check could be Fanfiction.net. There are many different categories and stories on this site. However, the search might need to be a bit more refined as there are so many works. But it's definitely worth a try to find those Brenda and Thomas kiss stories.