Are you referring to in a navigation? If so look into the $Menu template variable http://doc.silverstripe.org/framework/en/howto/navigation-menu. You can use it to recursively loop through all the child pages on the site if you pass in a bigger integer for the argument you get access to deeper levels of the nested structure e.g. $Menu(1), $Menu(2) I'd suggest having a play and experimenting to get your head around how these and template loops can work together.
You can of course also use the $Children variable while already within the scope of a Page's $Children.