Norman was the second child of the Burton family. However, due to his decision to found the Dunbar family and the fact that he and his older brother had a strained relationship, he was disowned and burned off the family tapestry.
Norman Dunbar lived in the twelfth century and excelled in Potions and Herbology. Due to being born as the second son in the Burton family, he didn't become the Head of the family after his father passed away but his older brother did. However, Norman and his older brother couldn't stand each other. Not wanting to answer to his older brother when he became the new Head of the family, Norman decided to found the Dunbar family and became its patriarch.
Norman's brother didn't take kindly to the fact that his brother founded a new family and saw this as treason. For this reason alone, he burned him off the family tree and disowned him.