Hi Elis,
The DirectedTree Layout can not be used for your requirement as the nodes do not have unique parent node.
To have layouting in a parent-child relationship, we need to use HierarchicLayout Manager.
My sample is located at the following location for your use:
http://websamples.syncfusion.com/samples/Diagram.Windows/F78790/main.htmLet me know if you shall need any further clarifications here.
Happy Coding!
-Ajeet