Hi Samson,
I couldn't able to understand your issue exactly, but nodes will stacked only when a single node has two parents(i.e two incoming connector to it). Please download the sample from the link provided below which does radial layout by using the data fetched from the database.
http://help.syncfusion.com/support/Diagram.Web/Forums/F91445/Diagram_ASP_DB_Radial.zipRegards,
Dinesh