Hi,

in my experience it is not directly possible to create a relationship from one object (entity) to itself. You need to introduce an additional node to which you reference from the entity and reference back to the entity.
                                                 __________  
                                                |       Entity    |
                                                |___________| 
                                                        /|\         |
                                                         |         \|/
                                                         |_____O New Node

Have a look at the UML example there you find a class called associationnode in the class diagram that is what you need to implement in your scenario.

Best wishes, Thomas