Black Best Friend: The sons are friends with the son of a Liberian consul, who's an outsider in Nazi Germany just like them. (His Real Life counterpart later became chief editor of the Ebony magazine!)
Brother-Sister Incest: Is the case with the neighbors of the Bertinis. The sounds they can hear through the thin walls allow the conclusion that the brothers are raping their sister.
Dysfunctional Family: The Series was actually toned down, but in the novel... Giacomo Bertini rapes his wife and openly cheats on her, Alfredo Bertini is definitely abusive, Recha is the worst kind of shrew, and the sons also have their problems, understandably. Oh, and during the war when they're hiding, as if they hadn't enough trouble, Lea gets pregnant and later gives birth to a baby girl, which is mongoloid.
Fat Bastard: One of the teachers (appropriately nicknamed "Speckrolle", 'roll of bacon') of Cesar and Roman Bertini, who's a radical nazi and works hard to make his class "free of Jews".
The Gestapo: Cesar gets taken and beaten up by them. When they release him, he learns that he also was kicked out of school.
Hooker with a Heart of Gold: Averted, if not inverted. Roman goes to a whore, who takes the ring he inherited from his grandfather as payment.
Informed Judaism: Mother Lea and grandmother Recha are technically Jews, but don't care much for their religion. Unfortunately, The Nazis also persecute Jews who don't care much for their culture/religion.
Likes Older Women: Roman Bertini with his neighbor Erika Schwarz, who'll help them later, being the main example of this.