I also would like to share some of my Airtags with my family. My Wife and I share the car keys and we are constantly upset with one another as we both leave the keys in all sorts of places.
From what I understand, if I was the owner of the tag only I can find the keys??? My wife cannot on her phone....this is such a shame as it would be most useful.. I can find her phone if she leaves it somewhere, and she mine... but not an Airtag ??
Also I would want both my wife and I to be able to update the position of the 'shared' Airtag. So if she say left the keys somewhere, her phone would have updated the last know location. This is also a feature I fear is not present currently...
Perhaps this is all coming in IOS 15... they are locking it down initially so we , the public get comfortable with the platform as it is and then they slowly open it up a little ? one can only hope...
A.