Why does Ernie Bully Calbert?

Calbert wonders why he is Ernie’s favorite victim at school. He learns from Roland, his trusted friend that Ernie’s dad died a couple of years ago, and Chuck, his step dad doesn’t really like him mostly because Ernie  looks like his real dad, and he has the same name as him. It makes Chuck jealous of Ernie’s dad. Sometimes he gets really mad at Ernie for no reason. He doesn’t have any true friends except for Munch, his pet dog.