JPA direct join to entities with common primary key

Question

Assume I have dozen of one-to-one relation using common id carId and I can't touch schema or merge them into one.

@Entity
public class Car {
  @Id
  private Integer id;

  @OneToOne(mappedBy="car")  
  private Registration regist;

  @OneToOne(mappedBy="car")  
  private Detail detail;

  @OneToOne(mappedBy="car")  
  private License license;
}

@Entity
public class Registration {
  @OneToOne
  private Car car;

  private String governor;
}

@Entity
public class Detail {
  @OneToOne
  private Car car;

  private Date manufacturingDate;
}

@Entity
public class License {
  @OneToOne
  private Car car;

  private String licenseNumber;
}

// and more ...

When I create a query begin with License to get data from Detail and Registration, the generated sql looks like

select
    car_detail.manufacturing_date,
    car_registration.governor
from
    car_license
left outer join
    car
        on car_license.car_id=car.id
left outer join
    car_detail
        on car.id=car_detail.car_id
left outer join
    car
        on car_license.car_id=car.id
left outer join
    car_registration
        on car.id=car_registration.car_id
where
    and car_license.licenseNumber=?

It's reasonable because JPA doesn't understand column car_id is common across entities. However, the result is hard to debug and error prone on complicated join.

How can I define those entities so that JPA knowns they don't need additional join on table car and can be joined directly, or just join to table car only once?