What is Kotler and Shmuel characters?

Kotler is one of the Nazi soldiers stationed at Out-With. He has "very blonde hair, an almost unnatural shade of yellow" (18). Gretl develops a crush on him, and it is implied that he is carrying on an affair with Mother. He is cruel and Bruno doesn't like him. Shmuel is the boy Bruno meets through the fence at Out-With. He is a prisoner and must wear the "striped pajamas" all the other prisoners wear. He shares a birthday with Bruno and they become friends.