Try this code.
private void test_Load(object sender, System.EventArgs e)
{
DataSet d = ds();
this.gridDataBoundGrid1.DataSource = d.Tables["Customers"];
GridHierarchyLevel childrenLevel = this.gridDataBoundGrid1.Binder.AddRelation("CustomerQ");
}
You can see sample usage in the three samples that you can find in this folder:
\Program Files\Syncfusion\Essential Suite\Grid\Samples\DataBound\Hierarchical