Heiser Brooket

Backstory

As a young lad, Heiser often got bullied quite a bit.  One because of his German heritage, and two because he was very strange. 

One time, when he was seven or so, he tripped on a doorframe. He should have fallen down, but instead, he floated right back up.

His brother, Thomas, saw the incident and tried to tell their mother, claiming "Theresa is a Witch!" (Heiser was known as Theresa during this time, however, he has since discovered his true identity).

His parents said that they did not believe Thomas, saying he was just making up lies for attention.

Later in life, at age 10, he made Thomas fly out of a second story window for bullying him for being transgender, saying "You aren't a man! Just look at your own chest, f****t!"

Thomas had broken several of his bones. In their sympathy for Heiser, they covered up the story so everyone would believe it to be an accident.

It all made sense to Heiser when he received his Hogwarts invitation letter. 

When Heiser went to Diagon Alley, he had an encounter with a werewolf who had grown more feral, as it was close to the full moon. The werewolf couldn't take it anymore and bit Heiser.

Since then, his 'furry little secret' as referred to by his friends, has been kept under wraps.

Or, at least, mostly.