The relationship between Harry and Snape would change drastically. Normally, they had a very strained relationship in the original story. But with Snape deaged, Harry would see him more as a vulnerable being in need of help. He might feel a sense of protectiveness towards Snape, which is a complete turnaround from his previous feelings. As for Ginny, she would probably approach Snape with an open mind. Her relationship with Snape would be more of a nurturing one, like taking care of a lost child. And between Harry and Ginny, their relationship could be strengthened as they share this unique experience of looking after Snape.
A plot could involve Snape's deaging being the result of a dark magic experiment gone wrong. Harry and Ginny initially suspect foul play but soon realize that Snape is truly a child in mind and body. They decide to protect him from those who might want to use his situation for their own gains. As they do so, Snape begins to form a bond with them, especially with Ginny, who he sees as a sister - like figure. Harry, meanwhile, has to deal with his own mixed feelings towards this new Snape, as he is constantly reminded of the old, often - hated Snape, yet also sees the potential for a new beginning.
Snape's personality would likely soften. He'd have to be more patient and understanding. Instead of just being the strict and often sarcastic Potions master, he'd become more nurturing. He'd still have his sharp edges, but around Harry, he'd show more kindness and care as he takes on the role of a guardian.
With his colleagues, like Dumbledore. When de - aged, Snape might be more open and less guarded. He may share his true feelings and thoughts more freely. Dumbledore might have to take on a more fatherly role towards him, guiding him through the challenges of being de - aged. And with the other Hogwarts professors, he could form new alliances or rivalries based on his new, younger self.
Snape's deaged personality could also be more impulsive. Without the restraint of his adult self, he might act on his emotions more quickly. For example, if he felt wronged, he might lash out immediately instead of plotting a long - term revenge like his older self would do. Also, he could be more curious about the world around him, eager to explore magic in a new way that his older self had forgotten due to years of being jaded.
In some fanfictions, they start off as bitter enemies as in the original story. But as the plot progresses, they might find common ground. For example, if there's a threat to Hogwarts that's bigger than their personal grudges, they may work together and their relationship turns into a more respectful one.
It would become much more complex. Snape, who is usually a solitary and somewhat brooding character, would have to step up and be more involved. Ginny, being young and from a different generation, might expect different things from him. Their relationship would likely face a lot of external pressure from the wizarding community too.
His personality would likely become more impulsive. As a 16 - year - old, Snape wouldn't have the self - control he developed over the years. He might be quicker to anger and less guarded in his emotions.
He might be more vulnerable. At 16, Snape was still developing his tough exterior. So, he could show more of his insecurities, especially when it comes to his family situation and his budding feelings for Lily. He might also be more impulsive, not having fully developed the self - control he had as an adult.
If Severus Snape adopted baby Harry Potter in fanfiction, it would completely transform the story. Firstly, Harry would grow up in a very different environment. Snape, being a strict and complex character, would likely raise Harry with high expectations in academics, especially in Potions. Harry might become more introverted under Snape's influence as Snape isn't the most sociable person. Also, Snape's knowledge of the Dark Arts could either protect Harry better or put him in more danger, depending on how Snape chose to use it in Harry's upbringing. The relationship with the other characters would be different too. For example, Harry's relationship with the Weasleys might not be as strong as in the original story since he would be growing up in a more isolated environment with Snape.
The relationship between Five and the others would be really interesting. Five, who is usually the most independent and aloof as an adult, would be forced to rely on his siblings as a child. He might be more vulnerable and in need of their protection. The other siblings would have to take care of him, which could change their perception of Five. They might see a side of him that was hidden before. And for Five, he might develop a newfound respect and closeness to his siblings as he experiences their care and love in this new, deaged state.