It could be Mat. He has a complex relationship with Mariana in the show, and a pregnancy between them would add a whole new layer of drama to their relationship. They've had their ups and downs, and this would be a major turning point.
Another possibility is that it could be a character from Mariana's past that we haven't seen much of in the show. Maybe an old friend or acquaintance who resurfaces in her life and is the father, bringing back old memories and emotions as she copes with the pregnancy.
Perhaps it could be a new character introduced specifically for the fanfiction. This new character could be from a different background or have different motives, which would create an interesting dynamic as Mariana has to navigate her relationship with him while also dealing with the pregnancy.
It could be one of her close friends or someone she has a romantic relationship with in the show. For example, it might be Brandon. Their relationship has been complex in the series, so it could be an interesting twist.
One possible storyline could be Mariana dealing with the reactions of her family. The Fosters family is very close - knit, and her pregnancy would likely cause a stir. Her moms might be initially shocked but then become very supportive, guiding her through the process of making decisions about the future, like whether to keep the baby or consider adoption.
Often, the theme of sisterhood is prominent. They support each other through various challenges in life. And also, the theme of social issues like discrimination in the foster care system. The rated M aspect might come from the complex and sometimes dark portrayals of these issues. For example, when they face unfair treatment from authorities or other kids, the story might get intense and thus be rated M.
To write a great 'The Fosters - Mariana' rated M fanfiction, start with a solid plot idea. Since it's M - rated, you might be dealing with more serious or adult - like themes. Think about how Mariana would react in these situations. Maybe she's facing a moral dilemma that's more complex than what's shown in the show. Use vivid descriptions to bring the story to life, but also be respectful of the source material and the character. Don't make her do things that are completely out of character just for the sake of the M rating. Develop the other characters in the story as well, as they can impact Mariana's journey.
I'm not sure specifically which rated M fanfictions about Mariana from 'The Fosters' are popular. However, you could start by looking on fanfiction websites like Archive of Our Own. They usually have a rating system in place, and you can search for 'The Fosters' and then filter for Mariana - centered stories with an M rating. Just be aware that M - rated stories may contain more mature themes such as violence, strong language, or sexual references.
Maybe it's a new character introduced just for this plot twist. This would add an element of mystery and new drama to the story.
It could be Ron. Since they have a relationship in the original story, it's a very likely option. Their relationship could be further developed as they face the new chapter of becoming parents together.
Perhaps it's a human boy who accidentally wandered into the fairy world. Tinkerbell, being curious, interacted with him, and in a magical turn of events, she became pregnant. This would create a lot of drama as the fairy world and the human world don't usually mix in such an intimate way, and there would be a struggle to figure out how to handle this situation.
It could be her long - time boyfriend. They might have been planning for a family in the future, but the pregnancy comes as a bit of a surprise earlier than expected.
Another possibility is that it's a result of some sort of experimental jutsu gone wrong. So there may not really be a traditional 'father' in the sense, but rather it's a consequence of Naruto's own actions in the world of ninja magic.