Can you set custom ringtones for contact groups? In iPhone, you can easily change the default ringtone (Settings → Sounds → Ringtone) and set a custom ringtone for individual people (Contacts → [some person] → Edit → Ringtone). 

But can you set a custom tone for a group of contacts? (E.g. "family" or "workmates".)

I think that would be handy—and quite basic functionality, so to speak—but I couldn't find a way to do this through the iPhone UI. Is it possible at all (without jailbreaking)?
It is unfortunately not (yet or ever?) officially supported as a feature of iOS.