Disclaimer: these aren't really necessary, I looked it up
Harry grew up nicely with the stable home that Peter, Margaretta, and his cousins provided. Her wore expensive suites and robes and went to the best school's money could buy. He proved to be quite the mischief maker. He usually planned the schemes and his cousins Galatea and Persephone went along with them. There was one thing that Peter was keeping from Harry. Harry had a sister named Portia who Peter had given to his friend Addie to care for. Addie had been taken dreadfully ill which was not an unusual occurrence for her. This time however it looked like her time was coming. With her time coming came his daughter Portia. He felt that the time for Harry to meet her was then.
"Have you been informed?" asked Persephone her face illuminated by the light of the gas lamp. Harry was confused and shook his head no.
"Don't tell him! It's supposed to be a surprise." Said Galatea. She sighed as she ran a brush through her long black hair. She was the oldest at twelve years old and because of that she felt like she was the most mature and the final authority on everything. Her mother held a secret from her that she was desperate to unravel, it was the mystery of her hair color. Black was not a normal hair color in the Pettigrew family and on the island as well. Harry asked her once and she said that she didn't know so he unwittingly started all of her curiosity. Well, she had been curious before but not to that extent.
"Well I'm sorry queen Galatea! Next time I'll ask your permission before I speak." Said Persephone taking a bow. Galatea shoved her and she pulled Galatea's hair. After that they quickly gained their composure.
"What is?" asked Harry looking over his book. He was trying to figure out how it would be possible to get off the island without anyone knowing for just a bit. He was very grateful for the life he had and all of his wonderful things but he was longing for the world outside of the island that he read about in books. Galatea also longed for the world outside of the island but Persephone seemed to have no urge to leave.
"Our cousin Portia." They both said in union. Persephone began to braid her long blonde hair as she thought of having another girl in the house. She had never really been allowed outside save for the few times she had snuck out at night. The only new people she met we staff and they were never very friendly.
"We have another cousin?" asked Harry looking up from his book and rubbing his eyes. Reading in the dim light of Portia's gas lamp put a terrible strain on his eyes and he wondered how she could live like that.
"Me and Persephone do." Said Galatea in a superior voice. Harry and Persephone were used to it being ten and nine respectively. This confused Harry greatly and he could only scratch his head. The only explanation that he could think of was that this Portia was his sister. He recalled his father saying something about a sister when he was very young but he wasn't sure if it was a real memory.
"What do you mean by that?" asked Harry bumping the gas lamp with his foot. Galatea caught it and sighed deeply. Persephone rolled her eyes at her older sister and Harry did the same. She always sighed when she felt that others were asking stupid questions.
"I mean that she is your sister, Harry. She is your twin sister. Mother told us about her but we weren't supposed to tell you. Please do try and act surprised when she gets here and act like you have no idea that she even exists. Much obliged." Said Galatea patting him on the back condescendingly. Harry thought that she was kidding and it was all just an elaborate joke. He left Persephone's room to get to the bottom of everything. He knew that his father was the person to ask since he'd probably know if he had any children he neglected to tell Harry about.