Hi there @MrIsItReAL,
thanks for posting !
Spotify has different subscription types which allow different access to the apps features.
In order to have more info which features are allowed on each subscription please make sure to check out this info page.
The major difference between having a Free account and a Premium subscription is that if you have Premium, you can use Spotify anywhere in the world for as long as you like as stated here.
However, if you permanently move to another country, you need to update your payment method to one that's issued in your new country.
To sum things up, if your family member is visiting another contry for any puprose he will be able to use Spotify (Premium) for as long as he likes.
But, if we're talking about moving to another country, he will have to change the country settings and provide a matching payment method for his Premium to work properly.
Hope this helps,
Let me know if you have any further questions