How to create a child page that has the same content type as parent page?
I found a module that does the job, which is Book made simple. This module add the setting on content type and have the option for "SELECT CONTENT-TYPES ALLOWED AS CHILD.", "SELECT CONTENT-TYPES ALLOWED AS PARENT" and "Other Settings". Then a dropdown listbox will be added in the books link like the one on screenshot. I hope Drupal 8 has a similar feature like this. 

PS: One of the issue is "Printer" module also print "Add child page" on each page.