How to share an AirTag with family members
You cannot share the location of an AirTag with other people.
The only privilege currently granted is indefinite silencing of AirTags owned by family members:

If the AirTag is attached to an item you're borrowing, you can tap
Pause Safety Alerts to turn off &quot;AirTag Detected&quot; notifications for
one day. If you're borrowing an AirTag from a member of your Family
Sharing group, you can turn off Safety Alerts for one day or
indefinitely.

https://support.apple.com/en-us/HT212227