No. In the original 'Harry Potter' books, there is no evidence to suggest that Severus Snape is Voldemort's son. Snape was a Death Eater who later turned spy for Dumbledore. His relationship with Voldemort was one of enmity in the end, and his loyalty was more towards Lily Potter and Hogwarts.
There is absolutely no evidence in the books for this. Snape's family background is explored to an extent, and he has his own story independent of being related to Voldemort. His love for Lily was a major driving force in his actions, not any supposed relation to Voldemort.
In fanfiction, evidence is often created within the author's own narrative world. Usually, the author might create some backstories or magical connections to suggest Snape is Voldemort's son. For example, they could fabricate a hidden relationship between Snape's mother and Voldemort in the past. But in the official 'Harry Potter' canon, there is no such relation at all.
In most fanfictions, the evidence is often fabricated within the fictional narrative created by the author. It could be things like hidden memories, secret meetings in the past that were never revealed in the original series, or some magical bond that was only known to a few. However, in the original 'Harry Potter' canon, there is no such relationship between Harry and Snape.
Often, fanfictions that claim Hermione is Voldemort's heir will create some convoluted backstory. For example, they might say that there was a secret affair between a distant relative of Hermione's and one of Voldemort's ancestors. This would then be used as the basis for her being his heir. However, this is pure invention for the sake of the fanfiction and has no basis in the real Harry Potter story. The original story has no such indication, but fanfiction allows for these wild and imaginative ideas to be explored.
Some plots might involve Snape being forced to confront his new - found relation to Voldemort in the middle of the wizarding war. For example, he could be captured by Voldemort's forces and Voldemort reveals the truth to him. Then Snape has to decide whether to embrace this new identity or fight against it. There could also be a plot where other characters like Harry and Hermione suspect Snape's relation to Voldemort and try to prove it.
Well, in some 'snape is harry's father fanfiction', the evidence could be Snape's complex emotions towards Harry. He's often shown as having a deep, unexplained connection. However, this is completely different from the official story. The fanfiction might twist the timelines or create new magical elements to support this relationship. For example, it could suggest that Snape had a relationship with Lily before James Potter and some sort of magic made it so that he was Harry's true father, but it's all just creative and not based on the original lore.
In some fanfictions, they might create evidence like Snape secretly protecting Harry more out of a fatherly love. For example, his constant watch over Harry at Hogwarts could be seen as more than just a teacher - student relationship. But in the original books, there is no such indication.
In most of the normal Harry Potter fanfiction concepts, this is a very unorthodox and against the general theme idea. There is no evidence in the original books to support such a relationship, so in this fanfiction, it's likely just a very creative and out - of - the - box fictional construct without any real evidence from the source material.
Yes, in some of those fanfictions, the evidence could be things like Snape's long - standing protection of Harry. The idea is that this protection might be more than just a sense of duty to Lily. It could be a fatherly instinct. Also, some fanfics might play with the idea of a magical spell or potion that changed the apparent paternity. But remember, this is all part of the fanfiction world and has no basis in the official 'Harry Potter' canon which firmly states that James Potter is Harry's father.
In most of the fanfiction exploring this concept, evidence is often fabricated within the alternate universe created by the author. It might be things like Snape secretly protecting Harry out of a fatherly love that is more intense than just a teacher - student bond. However, in the original 'Harry Potter' series, there is no such indication.
In most official 'Harry Potter' lore, Harry Potter is not Snape's son. However, in a fanfic, the author might create their own evidence. It could be things like Snape secretly having a relationship with Lily before she was with James. Maybe there are hidden moments of Snape showing father - like care for Harry that are not obvious in the original books. But these are all fabrications within the fanfic world.