help pls

public class Solution {
    public static void main(String[] args) {
       Human Grandfater1 = new Human("Иван", true, 60);
        Human Grandfather2 = new Human("Петр", true, 65);
        Human Grandmother1 = new Human("Антуанетта", false, 57);
        Human Grandmother2 = new Human("Елизавета", false, 60);

        Human Father = new Human("Александр", true, 40, Grandfater1, Grandmother1);
        Human Mother = new Human("Екатерина", false, 38, Grandfather2, Grandmother2);

        Human Sun = new Human("Сергей", true, 16, Father, Mother);
        Human Daughter1 = new Human("Анна", false, 14, Father, Mother);
        Human Daughter2 = new Human("Яна", false, 18, Father, Mother);

        System.out.println(Grandfater1);
        System.out.println(Grandmother1);
        System.out.println(Grandfather2);
        System.out.println(Grandmother2);
        System.out.println(Father);
        System.out.println(Mother);
        System.out.println(Sun);
        System.out.println(Daughter1);
        System.out.println(Daughter2);
    }

    public static class Human {
        String name;
        boolean sex;
        int age;
        Human father;
        Human mother;

        public Human(String name, boolean sex, int age){
            this.name=name;
            this.sex=sex;
            this.age=age;
        }

        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 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; } } }