Почему не добавляются дети ?

package com.javarush.task.task08.task0824; import java.util.ArrayList; import java.util.Collections; import java.util.List; /* Собираем семейство */ public class Solution { public static void main(String[] args) { Human child1 = new Human(); child1.name = "Федор"; child1.sex = true; child1.age = 7; Human child2 = new Human(); child2.name = "Клава"; child2.sex = false; child2.age = 3; Human child3 = new Human(); child3.name = "Lexa"; child3.sex = true; child3.age = 3; Human father = new Human(); father.name = "Емельян"; father.sex = true; father.age = 30; father.children.add(child1); father.children.add(child2); father.children.add(child3); Human mother = new Human(); mother.name = "Зинка"; mother.sex = false; mother.age = 27; mother.children.add(child1); mother.children.add(child2); mother.children.add(child3); Human grandfather1 = new Human(); grandfather1.name = "Борис"; grandfather1.sex = true; grandfather1.age = 60; grandfather1.children.add(mother); Human grandfather2 = new Human(); grandfather2.name = "Федор"; grandfather2.sex = true; grandfather2.age = 65; grandfather2.children.add(father); Human grandmother1 = new Human(); grandmother1.name = "Клава"; grandmother1.sex = false; grandmother1.age = 60; grandfather2.children.add(mother); Human grandmother2 = new Human(); grandmother2.name = "Фрося"; grandmother2.sex = false; grandmother2.age = 63; grandfather2.children.add(father); System.out.println(child1.toString()); System.out.println(child2.toString()); System.out.println(child3.toString()); System.out.println(grandmother1.toString()); System.out.println(grandmother2.toString()); System.out.println(grandfather1.toString()); System.out.println(grandfather2.toString()); System.out.println(mother.toString()); System.out.println(father.toString()); } public static class Human { String name; boolean sex; int age; ArrayList <Human> children = new ArrayList<>(); public String toString() { String text = ""; text += "Имя: " + this.name; text += ", пол: " + (this.sex ? "мужской" : "женский"); text += ", возраст: " + this.age; int childCount = this.children.size(); if (childCount > 0) { text += ", дети: " + this.children.get(0).name; for (int i = 1; i < childCount; i++) { Human child = this.children.get(i); text += ", " + child.name; } } return text; } } }