Snape's character changes in his relationship with others too. He becomes more involved with the Hogwarts community as he is now responsible for Harry. He might start to collaborate more with other teachers, like McGonagall, who he previously had a rather cold relationship with. His attitude towards the students also changes as he realizes that they are just kids trying to find their way, much like Harry. This is a big shift from his usual strict and often unforgiving self.
In this fanfiction, the story could start with Harry finding Snape in a very vulnerable state after the Battle of Hogwarts. Harry feels a deep sense of guilt for how Snape was treated throughout his life. So he decides to adopt him. At first, their relationship is awkward. Snape is still his old sarcastic self, but Harry is determined. As time passes, they discover they have a lot in common. They both lost their parents at a young age, and they both had to face great challenges. This newfound understanding leads to a transformation in their relationship. Harry helps Snape to come out of his shell of bitterness, and Snape teaches Harry more about the Dark Arts in a controlled and ethical way so that Harry can better protect the wizarding world in the future.
The relationship would start off rocky. Snape would be resistant to Harry's kindness as he has always seen Harry as James Potter's son. But Harry's persistent efforts to understand and help Snape would gradually break down Snape's walls.
In such a fanfiction, Harry might see the potential in young Severus that others overlooked. He could protect Severus from the bullies at Hogwarts. Harry, having experienced his own share of hardships, would understand Severus's situation to some extent and try to give him a better childhood, perhaps even guiding him to use his magic in a more positive way.
A really unique plot could be Snape adopting Harry during a time when Voldemort is still a threat. Snape has to balance protecting Harry from Voldemort's followers and also from the prejudice within the wizarding community. He might train Harry in Occlumency more intensively, and in the process, they develop a deeper understanding of each other. Harry starts to see Snape not as the mean professor but as a complex person with his own traumas and reasons for his actions.
In such a fanfic, Snape's parenting style might be strict yet protective. He would likely enforce high standards in Harry's magical studies, just as he does in the classroom. But at the same time, he would secretly keep Harry safe from any real threats. He might not show much affection openly, but his actions would speak volumes.
Severus could become more confident. With Harry's support, he may not be as shy or withdrawn as in the original story. He might be more open to making friends outside of Slytherin.
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.
Snape's parenting style would likely be strict. He is a no - nonsense person, so he would expect Harry to follow rules precisely. He would probably be very demanding when it comes to Harry's studies, especially in Potions. However, Snape also has a deeply emotional side, so he might be protective of Harry in his own way, though he would rarely show it outwardly.
A lot of fanfic writers will create unique storylines for Snape's courtship. They might introduce an original character who manages to break through Snape's tough exterior. His courtship would then involve him struggling with his own insecurities and his reputation. This character might see the good in him that others overlook. There could be moments of tension and misunderstanding, but also deep, meaningful conversations as they get to know each other better.