I have a parent site and a sub site . Each has separate lists with same content types. I need to add Content Query Web Part(CQWP) to the Parent Site and Perform Roll up from child site and display the list items in the home page of Parent Site. I need to do this using ONET.XML in my Custom Site Definition.Can any body share their knowledge regarding the web part code and settings that needs to be done in it for the specified content type. Thanks,

You need to create web part with needed definition to dummy site and export it. Then you need to take care of some tips I wrote in article below: http://sharepointserver-2007.blogspot.com/2012/06/use-content-query-webpart-with-site.htmlTarek Yehia