SOLVED !?!?!
After extensive testing (well actually, a few calls to family members), I have found that if both parties are running IOS 15.x and both parties have the "Find My" application running (even if in the background), then it will show you the "Live" location of the other party, however if the person you are trying to view does not have the "Find My" application running on their end, it will NOT show you their live location.
The other observation we made is that if you leave the "Find My" application running in the background, it does appear to significantly reduce your battery charge level, which I guess is to be expected if it is using your GPS to determine your position at a high frequency, and sending that data to Apple.
If you find that the above is not true in your situation, please feel free to reply and advise this was not a solution in your case.