Before her letter from Hogwarts, Hermione knew magic was real. Her parents always told her stories of wizards, witches, magical creatures, and special schools where you could learn how to use magic. Not that fake magic that you could watch on the telly.
Growing up, she would listen to her mother talk about amazing creatures. Little beings that would take care of every need you may never have. Horse-like creatures that had no hair and wings like bats, though these were hard to see because you needed something to happen before you could. When she would ask what she needed to do, her mother would softly smile and tell her that was a story for later.
The first time Hermione experienced accidental magic, her parents were surprised. She was 7, and she remembered being so proud of herself. She had made magic, even if it was just getting her book off the roof where the kids down the street threw it. It was still magic! She was just like the stories.
On her 11th birthday she got a letter. She was going to go to Hogwarts. An aged woman with a real-life witch's hat came to their door to explain more about her new life. That was the day her parents told her about the war. How a madman tried to take over the wizarding world and remove anyone that wasn’t pure-blooded, people without magic, people like her parents. They explained that their families were magical, but they were not. They were in fact something called a “Squib.”
People born into magical families but have no magic themselves. How they are normally cast out by their families as an embarrassment. Her father’s family didn’t do that. They protected him, loved him, and kept him safe. When by happenstance David Dagworth-Granger met and fell in love with fellow Squib Jean Figg, they protected her as well.
Until they couldn’t. The masked followers, her parent told her they were Death Eaters, came to their door. They knew the evil wizard would want them dead. It was pure luck that her parents survived and managed to escape; they had grabbed their infant daughter and fled to Muggle London and disappeared.