Программа правильная, но не проходит последнее условие валидатора. В чем может быть проблема?

package com.javarush.task.jdk13.task07.task0724; /* Семья */ public class Solution { public static void main(String[] args) { Human gf1 = new Human("Миша", true, 60); Human gm1 = new Human("Лена", false, 61); Human gf2 = new Human("Игорь", true, 62); Human gm2 = new Human("Лариса", false, 63); Human dad = new Human("Саша", true, 41, gf1, gm1); Human mom = new Human("Галя", false, 31, gf2, gm2); Human ch1 = new Human("Аня", false, 10, dad, mom); Human ch2 = new Human("Катя", false, 11, dad, mom); Human ch3 = new Human("Никита", true, 12, dad, mom); System.out.println(gf1); System.out.println(gm2); System.out.println(gf2); System.out.println(gm2); System.out.println(dad); System.out.println(mom); System.out.println(ch1); System.out.println(ch2); System.out.println(ch3); } public static class Human { private String name; private boolean sex; private int age; private Human father; private Human mother; public Human(String name, boolean sex, int age, Human father, Human mother) { this.name = name; this.sex = sex; this.age = age; this.father = father; this.mother = mother; } public Human(String name, boolean sex, int age) { this.name = name; this.sex = sex; this.age = age; } public String toString() { String text = ""; text += "Имя: " + this.name; text += ", пол: " + (this.sex ? "мужской" : "женский"); text += ", возраст: " + this.age; if (this.father != null) { text += ", отец: " + this.father.name; } if (this.mother != null) { text += ", мать: " + this.mother.name; } return text; } } }