This is expected behavior by the system. If you create a new page for example the page name will be the url and the child of the new page will have the name of its parent.
What I can suggest you as a workaround is to use a 3rd party URL Rewriter module. However if you use a rewriter, it should iterate over all the pages you want to change and for each additional url of a page generate a string like that:
If you need any further assistance, feel free to write back.
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