Is it possible to create parent and sub-category fields in profile?

Is it possible to create parent and sub category custom field in profiles? I need to create a parent select field and depending on what is selected, it presents a second set of fields?

I want it to work like the country field, and see that in country field I can set the source to a file, would it cause problems if |I used the country field for my purpose?

Kind regards

Mel