Hello.
If the child page uses the same template as its parent, all content from parent´s page template is inherited to its child. Content of some web parts (EditableText, EditableImage) is bound to document, so the web part is inherited, but content not.
I would recommend you to consider Visual inheritance model (
http://devnet.kentico.com/docs/devguide/visual_inheritance.htm) and do a proper documents structure.
Best Regards,
Radek Macalik