Who turned out to be the brother of the two young boys in Valley Forge Maniac Magee?

In "Maniac Magee" by Jerry Spinelli, the two young boys who are brothers are named Amanda and Mars Bar Thompson. They are part of the Thompson family, and their dynamics play a role in the story as Maniac Magee navigates his interactions with them. The brothers, particularly Mars Bar, initially have a confrontational relationship with Maniac but later undergo character development.