Выдает ошибку - Exception in thread "main" java.lang.NullPointerException: Cannot read field "name" because "this.father" is null

public class Main {

  public static void main(String[] args) throws IOException {
    BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));

    String oldCatFather = reader.readLine();
    Cat catOldFather = new Cat(oldCatFather);

    String oldCatMather = reader.readLine();
    Cat catOldMather = new Cat(oldCatMather);

    String father = reader.readLine();
    Cat catFather = new Cat(father,catOldFather,null);

    String mather = reader.readLine();
    Cat catMather = new Cat(mather,null,catOldMather);

    String son = reader.readLine();
    Cat catSon = new Cat(son,catMather,catFather);

    String daughter = reader.readLine();
    Cat catDaughter = new Cat(daughter,catMather,catFather);

    System.out.println(catOldFather);
    System.out.println(catOldMather);
    System.out.println(catFather);
    System.out.println(catMather);
    System.out.println(catSon);
    System.out.println(catDaughter);
  }

  public static class Cat {
    private String name;
    private Cat father ;
    private Cat mather;

    Cat(String name) {
        this.name = name;
    }

    Cat(String name, Cat father ,Cat mather) {
        this.name = name;
        this.father = father;
        this.mather = mather;
    }

    @Override
    public String toString() {
        if (name ==  null && name == null){
            return "The cat's name is " + name + ", no mother, no father";

        }
        else if (father == null){
            return  "The cat's name is " + name + ", no mother,  father is" + father.name + "";

        }
        else if (mather == null){
            return  "The cat's name is " + name + ",  mother is "+ mather.name + ", no father";

        }
        else  {
            return  "The cat's name is " + name + ",  mother is "+ mather.name + ",  father is" + father.name + "";
        }
    }
  }
}

НЕ ПОНИМАЮ КАК ИСПРАВИТЬ СПАСИБО ЗА ПОНИМАНИЕ