The main characters in Sucker are two Southern, farm-raised teenagers. Peter, the oldest, is 15 years old while Sucker is 12, although sometimes he is described as being "four years younger".
Pete is the alpha. He is always in charge of starting and ending conversations with Sucker. He is also verbally abusive to Sucker and likes to humiliate him just like he gets bothered and humiliated by a girl named Maybelle at school. Pete uses Sucker as his emotional punching bag, and was nice to him only one time. In the end, we see that it is Sucker, and not Peter who ends up growing bigger and worse than Peter.
Sucker is the cousin and later adopted family member of Peter's. He is obviously traumatized, shy, and scared. He is no initiator and is co-dependent on the attention and care of Peter, who offers him none. Sucker has obviously been holding back something internal that Peter pretty much brought out of him one specific day when Peter insulted Sucker very badly. After that, Sucker all of a sudden grew into a big, bad man, threatening Peter with his very look, and making us wonder if he is real or not.