Hello,
Thanks for contacting us and sorry for any inconvenience that might have been caused due to that.
You don’t have to create a sitemap of the parent page including the sub-pages to inform Google about the parent-child relationship of your pages. Google will be able to detect that by your sub-pages’ URL structure.
We divide the sub-sitemaps based on the post type and that’s why you are seeing sub-pages in the page sitemap as they are also pages. And it doesn’t matter if it is under a sub-sitemap or main sitemap, the main use of the sitemap is to submit the URL to Google, they decide how to treat the pages/posts after crawling them.
If you still want to create a custom sitemap then you can follow this guide: https://rankmath.com/kb/custom-sitemaps/
Hope this helps. Let us know if you need any other assistance.
Hello,
Since we did not hear back from you for 15 days, we are assuming that you found the solution. We are closing this support ticket.
If you still need assistance or any other help, please feel free to open a new support ticket, and we will be more than happy to assist.
Thank you.
