Who is Miss Trunchbull from Matilda and what is their importance?

Matilda's brother Michael is very different than his sister. Like his father, he is interested in the business of cheating people out of their money and he does not question the morality of what his father is teaching him. However, it would be unfair to expect anything else from him considering who his parents are and what he has been taught. He is a minor character in the story, so there is not too much information about him, but he does not ever mistreat Matilda, even though his parents would probably allow him to. When the family moves to Spain without Matilda, he is the only one to turn around to say goodbye.