Hogwarts

On the night Voldemort attacked the Potters' home in Godric's Hollow, there were two children in the house: one-year-old Harry and his younger sister, who was not yet a month old.
After the deaths of James and Lily, the wizarding world celebrated the fall of the Dark Lord, but only a few knew that Harry had a sister. To protect the girl from the remaining Death Eaters, her existence was kept a secret. Harry was sent to the Dursleys, and the girl was placed with a wizarding family under the supervision of the Potters' old friends.
And so, brother and sister grew up, completely unaware of each other.
At eleven, Harry received a letter from Hogwarts and was sorted into Gryffindor. There, he befriended Ron and Hermione, became the youngest Seeker in a century, uncovered the secret of the Philosopher's Stone, and helped stop the return of Voldemort.
A year later, new first-years arrived at Hogwarts.
Among them was a girl with long reddish-brown hair and brown eyes. In appearance, she was almost an exact copy of Lily Potter: the same soft features, a kind smile, and a gentle grace. From James, she inherited the brown eyes, unruly hair, and a bit of his stubbornness.
During the Sorting, the Hat almost immediately shouted:
— GRYFFINDOR!
The faculty table erupted in applause.
As the girl sat down at the table, many students looked at each other in surprise. The older students, who had seen old photographs of Harry's parents, couldn't shake the feeling that a young Lily Potter was standing before them once again.
Harry himself also noticed something familiar in her appearance, but he couldn't quite put his finger on what it was.
Only Headmaster Dumbledore knew the truth. Sometimes he watched as the brother and sister sat side by side, not even suspecting that they were family.
And Hogwarts seemed to feel it: the moving staircases constantly bumped them into one another in the corridors, and the professors involuntarily remembered Lily every time they saw the new student.
No one yet knew that the ancient castle held one of the greatest secrets of the Potter family — the secret that the Boy-Who-Lived had never been the only child of his parents.