Isaac E. Hiltshire/Story

Before Hogwarts
Isaac grew up in London with his mother, a Muggle named Alice Hiltshire, and his biological sister, who looked up to him as a young child. His father, who is a wizard, left the family shortly after Amelia was born. Isaac's mother remarried to a man named Arthur Harrington, who has two young daughters named Abigail and Amanda.

Back home, Isaac was pressured into being an academic star in his school, but his rugged and rebellious personality was obviously not a good fit for this standard. He was forced to do things such as learn how to play the violin (which he slightly remembers how to do).

Because the other students disliked of his oblivious and loud nature, he found solace in the older delinquents at his school. He was introduced to them by his older next-door neighbor, Cooper. He was a bit of a "cabin boy" to the group, and he followed them around as they skipped school, stole things, got into fights, and played baseball or street hockey. He missed school and his music lessons to join their adventures, seeking their approval. Of course, they did not take him seriously due to his age and often peer pressured him to break rules, abandoned him in shady neighborhoods or stores, or made fun of him. They eventually hazed him by forcing him to physically fight a guy from another school. Isaac, being younger and weaker than everyone else at the age of ten, knew he had no way of beating an older boy from their rival school. As the opponent came in for a punch, he got electrocuted by Isaac’s arm trying to feebly block his fist due to his intense fear. An adult then found and yelled at everyone involved. Isaac’s group and the rival blamed the shock on Isaac’s “stupid wool sweater,” which Isaac decided to just believe as well.

Another significant event was Isaac and the delinquents sneaking onto someone's property to scare one of the guys' ex-girlfriend, but Isaac ended up frightening the ex-girlfriend's pet rabbit to death. The delinquents escaped with Isaac and faced no punishment, but he still continues to think about the night.

At some point, Isaac got expelled from his school, which he reveals to some of his Hogwarts classmates in his first year. Because he was unable to fulfill his mother’s expectations, she began to focus on his younger siblings instead, leaving him to do whatever he pleased, such as read comics and wander the city to visit arcades. Amelia began to despise Isaac.