Adding Subheader Rows into a Gridview

Question

This is a follow up from the sample i saw on this site;
http://www.carlj.ca/2008/04/20/adding-or-inserting-subheader-rows-into-a-gridview/

Now, i have two table i would like to combine and have same result as presented in the link above.

One of the tables is a parent table while the other references it.

Thank you.