Wrong behavior when I set the parent on the child, in an 1:m assoc

[L Eder]

Hi members:

I have a Skills entity that has two instances.
And i have Operador as its parent, and I created two instances of it.

I then add skill1 to operador1. However when I add skill1 to operador2,
then skill1 is moved to operador2 from operator1.

I would like both operador instances has both skill1.

I even tried this, without success:
public Operador add(

            @ParameterLayout(named="Habilidade a Adicionar") final Skill
skill){

        getSkilldeveloped().add(skill);



        return this;

    }

Any tips? Thanks in advance,

Source code
"
  -Operador.java-


@Persistent(mappedBy = "operador", dependentElement = "true")

                                   @CollectionLayout(render =
RenderType.EAGERLY)

                                   @Getter @Setter

                                   private SortedSet<Skill> skilldeveloped
= new TreeSet<Skill>();



                                   @Action(semantics =
SemanticsOf.IDEMPOTENT)

                                   public Operador add(


@ParameterLayout(named="Habilidade a Adicionar") final Skill skill){



                                        skill.setOperador(this);



                                       return this;

                                   }



                               -Skill.java-



                                   @Column(allowsNull = "true")

                                   @Getter @Setter

                                   private Operador operador;

                               "