@Entity @Table(name="house")
public class House extends BaseObject {

   private Long id;

   private String name = null;

   private String address = null;

   public House() {}

   @OneToMany (fetch = FetchType.LAZY, cascade = CascadeType.ALL)
   @JoinColumn(name = "fk_house_id")
   private List<HouseContact> houseContacts;

   public void addHouseContact(HouseContact houseContact) {
       if (this.houseContacts == null) {
           houseContacts = new ArrayList<HouseContact>();
       }
       this.houseContacts.add(houseContact);
       houseContact.setHouse(this);
   }

   public List<HouseContact> getHouseContacts() {
       return houseContacts;
   }

   public void setHouseContacts(List<HouseContact> houseContacts) {
       this.houseContacts = houseContacts;
   }

   ......
}

@Entity @Table(name="house_contact")
public class HouseContact extends BaseObject {

    private Long id;

    private String name = null;

    public HouseContact() {}

    @ManyToOne (fetch = FetchType.LAZY, cascade = CascadeType.ALL)
    @JoinColumn(name = "fk_house_id", nullable = false)
    private House house;

    public House getHouse() {
        return house;
    }

    public void setHouse(House house) {
        this.house= house;
    }

    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator="seq_house_contact")
    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

.....
}