Hi Shwetha,
You could use the CoveredRange support to merge two cells. Please refer this code snippet:
this.gridControl1[0,1].Text="Merging Two Cells";
this.gridControl1.CoveredRanges.Add(Syncfusion.Windows.Forms.Grid.GridRangeInfo.Cells(0,1,0,2));
Here is a sample.
mergingtwocells.zip
Please let us know if this helps.
Best Regards,
Jeba.