I'm searching at utilizing a custom template for some groups. Can you really make use of a category template (like category-4.php) on the parent category and also have the children use that template too?

So in line with the answer to date, it is possible to way to do this? I wish to add text and pictures to any or all groups inside a parent category.

In the documentation it doesn't seem to be possible without really adding several category template files (unless of course you custom program it). I run Wordpress, and that i only have seen it accomplished category by category.