Actually, I cannot reproduce the issue. I believe that when you have different parents, you could have duplicated pages. Find attached a screenshot that shows how it works on my project. If you still have the issue could you please elaborate a little bit more on what exactly you are doing, and what is preventing you from achieving the behavior I have on the screenshot.
All the best,
Do you want to have your say in the Sitefinity development roadmap? Do you want to know when a feature you requested is added or when a bug fixed? Explore the Telerik Public Issue Tracking
system and vote to affect the priority of the items