class A { 
  ID id; 

  @OneToOne ( mappedBy = "A", orphanRemoval=true, cascade = CascadeType.ALL) 
  B b; 
} 

class B { 
  ID id; 
  @NotNull
  @OneToOne (optional = false)
  @JoinColumn(name = "a_id", nullable = false, referencedColumnName = "id" updatable = true, unique = true)
  A a;
  @OneToMany ( fetch = FetchType.EAGER, cascade = CascadeType.ALL, orphanRemoval = true) JoinTable(name="B_to_C", joinColumns = @JoinColumn(name="B_id", referencedColumnName = "id"), inverseJoinColumns = @JoinColumn(name="C_id", referencedColumnName="id")) 
  Set<C> listOfCs;
}