How to determine if the active WordPress theme is a child theme
WordPress has the concept of child themes. In which case you should not delete the parent theme if your active theme is a child of that parent.
To determine if the currently active WordPress theme is a child theme, look at the top comment section of the style.css file of your active theme. If you see the “Template” property listed as in …
then that means that your theme is the child theme of the twentythirteen theme.
If you don’t see a Template property, that means your theme is not a child theme.