Hi Ramana,
Thank you for your interest in Syncfusion Products.
We could not reproduce your issue which you have mentioned. We have created sample that illustrates Parent-Child Table relationship. Let me know the sample which I have provided reproduces your issue otherwise please provide the modified sample. It will be useful for us for further analysis.
Please download the sample from below link
http://files.syncfusion.com/support/GGC.Web/7.3.0.20/F90218/Grid_Web_ParntChildTable.zipRegards,
Gowri