Perhaps it's a mysterious new character. This new character could be from a different part of the wizarding world, and Hermione got involved with him in a secret mission or something similar, resulting in the baby.
It could be Ron. Maybe they had a falling out or some complicated situation that led to Hermione keeping the baby a secret from him.
The father might be a character who is in a position of power and Sakura is afraid of the consequences if his identity is revealed. For example, he could be a nobleman or a powerful wizard in a magical world. Since having a relationship with him might be frowned upon or dangerous, she keeps the baby a secret.
It could be a powerful wizard who has been in hiding all this time. Maybe someone with a dark past that the author wants to explore.
Another possibility is Harry Potter himself. This would be a very different take on their relationship. In some fanfiction, the strong bond between Hermione and Harry could be taken to a new level. Maybe in a situation where they are the last hope for the wizarding world, they conceive a child in secret to carry on some special magic or power that could save the wizarding community.
Maybe the story could be about Hermione trying to protect the baby from dark forces in the wizarding world while keeping its existence a secret. She might have to face challenges alone without the support of her friends at first.
Maybe it's a mysterious character. The fanfiction could introduce a new character as the father, someone with a hidden past or special abilities that add an element of intrigue to the story.
It could be a character she has had a long - standing relationship with in the original story. Maybe someone who has been by her side through many adventures and they shared a deep emotional connection which led to the baby.
Perhaps the father is another well - known fairy in Pixie Hollow, like Terence. They could have had a secret relationship that led to the baby. Terence has always been close to Tinkerbell, and their shared experiences with pixie dust and helping Peter Pan could have deepened their connection to the point where they had a baby.
Perhaps it's a new character, a foreign traveler who came to Mulan's village. He was charmed by Mulan's strength and beauty, and they fell in love. He is the father of the baby in the fanfiction.
It could be Naruto. Given their relationship in the original series, it's very likely that he could be the father in the fanfiction.
Jace could be the father. Since they have a strong connection in the original story, it would make sense for him to be the father in the fanfiction.