import java.io.Serializable;
import java.util.List;
import java.util.Objects;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import org.hibernate.envers.Audited;

@Entity
@Audited
public class Parent implements Serializable {

    @Id
    private String id;

    @OneToMany(mappedBy = "id.parent")
    private List<Child> children;

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public List<Child> getChildren() {
        return children;
    }

    public void setChildren(List<Child> children) {
        this.children = children;
    }

    @Override
    public int hashCode() {
        int hash = 5;
        hash = 97 * hash + Objects.hashCode(this.id);

        return hash;
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj) {
            return true;
        }

        if (obj == null) {
            return false;
        }

        if (getClass() != obj.getClass()) {
            return false;
        }

        final Parent other = (Parent) obj;

        return Objects.equals(this.id, other.id);
    }
}

import java.io.Serializable;
import javax.persistence.EmbeddedId;
import javax.persistence.Entity;

@Entity
public class Child implements Serializable {

    @EmbeddedId
    private ChildId id;

    public ChildId getId() {
        return id;
    }

    public void setId(ChildId id) {
        this.id = id;
    }
}

import java.io.Serializable;
import java.util.Objects;
import javax.persistence.Embeddable;
import javax.persistence.JoinColumn;
import javax.persistence.JoinColumns;
import javax.persistence.ManyToOne;

@Embeddable
public class ChildId implements Serializable {

    @ManyToOne
    @JoinColumns({
        @JoinColumn(name = "parent_id", referencedColumnName = "id")
    })
    private Parent parent;

    private Integer number;

    public Parent getParent() {
        return parent;
    }

    public void setParent(Parent parent) {
        this.parent = parent;
    }

    public Integer getNumber() {
        return number;
    }

    public void setNumber(Integer number) {
        this.number = number;
    }

    @Override
    public int hashCode() {
        int hash = 5;
        hash = 79 * hash + Objects.hashCode(this.parent);
        hash = 79 * hash + Objects.hashCode(this.number);

        return hash;
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj) {
            return true;
        }

        if (obj == null) {
            return false;
        }

        if (getClass() != obj.getClass()) {
            return false;
        }

        final ChildId other = (ChildId) obj;

        if (!Objects.equals(this.parent, other.parent)) {
            return false;
        }

        return Objects.equals(this.number, other.number);
    }
}