Well, it's very probable. 'Shadowhunters' has a large and creative fan base. Given the popularity of the characters Clary and Alec, fans might be interested in writing about a moment like a kiss between them. However, the quality and nature of these fanfictions can vary greatly. Some might focus more on the emotional build - up to the kiss, while others might just include it as a part of a larger story arc.
Well, their relationship in the original series has a lot of potential for exploration in fanfiction. They start off as somewhat at odds with each other, but as they face common enemies and challenges, there is room for their relationship to grow and change in many different ways that fanfiction writers like to explore.
A plot could revolve around their family. They might decide to adopt a young Shadowhunter in need. This would bring out their parental instincts and also show how they support each other in raising the child. They could also face opposition from some in the Shadowhunter community who don't think they are suitable parents, but they prove them wrong through their love and determination.
There is a fanfiction called 'Alec's Perspective on Clary'. This one is interesting as it gives insights into Alec's thoughts about Clary. It shows how his initial wariness turns into a sort of begrudging respect and then friendship as they face different challenges in the Shadowhunter world.
Sure, many fanfiction writers have explored the idea of Alec and Clary getting married. Some fanfictions might show how they adapt to living together. Maybe Clary's artistic side could influence the decor of their shared home, while Alec's leadership skills could help them in making important decisions for their family and their role in the Shadowhunter society.
In fanfiction, their kiss could signify a change in their relationship dynamic. Maybe it's a turning point from just being comrades to having deeper, more complex feelings for each other.
One popular storyline could be how they deal with the challenges of being young and expecting in the dangerous world of Shadowhunters. They might have to face threats from demons while also preparing for the baby.
Alec would likely become more protective. His natural instinct to safeguard would intensify not just for Clary but also for their unborn child. He'd be constantly on guard against any potential threats.
You can try websites like Archive of Our Own (AO3). It has a vast collection of fanfictions, and you can easily search for Alec x Clary stories using the search function. Just type in their names, and you'll get a list of relevant fanfictions.
One popular Alec x Clary fanfiction might be those that explore their relationship in an alternate universe. For example, a story where they meet under different circumstances than in the original series. Maybe they're both on a secret mission together and start to develop feelings that way.