Sidebar Question?

I was just wanting to know if it was possible to show the “child” pages in the main “parent Page” inside the side bar.

Say for example you were looking at a personal/blogg type site, and you went to the Parent Page for information regarding the blogg author, and then listed in the sidebar you would see the other child pages…

Is this possible? As I do not want to show all the Pages, and Child Pages in the side bar, only when you are viewing the Parent page.

Is there a certain Code for that? I have came across a theme (Fauna – http://www.noscope.com/fauna/) that does this but it all seems very confusing to edit for my liking and such.