Gram and Grim, Max's grandparents, and the parents of his mother, take Max into their home in an attempt to get him to play with kids his own age and "improve his temper." Max himself seems to be quite suspicious of them and dislikes how they treat him. He particularly hates how they call him Maxwell when all the other kids have a nickname for him such as Mad Max and Max Factor.
Part of his distrust stems from the fact that they talk about him in negative terms while they think he's asleep. On one occasion Max overhears them saying that he is "getting to look like him," meaning Max's father. They obviously don't like his father because they state that if Max becomes anymore like him "we'd better watch out, you never know what he might do while we're sleeping."
The general feeling is that they are only taking care of Max out of feeling of responsibility and they can't over the fact that he is the child of someone they detest.