Is this to stop a husband following his wife’s every movement by tracking the tag on her keys? If so it makes perfect sense to me and is actually a good move.
Are you kidding me? If the wife wants to go places without husband knowing where she is (and vice versa), then it's time to get a divorce. You don't want to function like a family, don't enable family sharing. Family sharing can't be enabled without each member's consent. it's only for those under 18 that family sharing can be enabled without their consent, but then again, that comes with the territory of not being an adult.
If you enable family sharing, then family members should be okay with other family members knowing their location. If family members don't want to share their location, they shouldn't accept being invited into the family sharing.
Also, the AirTag is not the best way to track your family member. Find My allows you to track any device that has its Apple ID accepted into family sharing. Remote family can still share their location via the iPhone/Apple Watch, using Find My Friends (now called
People in the Find My app). AirTags are not for tracking people's location. It's for tracking the location of things and perhaps dogs unless you want to buy an iPhone for your dog.
If I want to track a key fob or a dog with an AirTag, and I am married, so both the car and the dog belongs to both my wife and me, then we should both be able to track the same AirTag.
Those who are talking about using AirTags to track their significant others are most likely not married. They are most likely tyring to overstep the boundaries of their current relationship, where the other party of the relationship thinks about it in much looser and freer terms than the party that is trying to leverage the AirTag to exert their control. If you want to know where your significant other is, talk to him/her and tell them that's what you want to do. They will either agree to enable Family Sharing or Find My Friends, or they will tell you to go jump in the lake, and then you will know the exact state of your relationship.
For my wife and me, Find My iPhone / Friends has been a huge blessing because in some cases, my wife may not hear the phone call (phone in her purse, Apple Watch is out of battery or phone left in the car), etc. or me not being able to answer the phone or not hearing it ring, both of us can locate each other quickly. I can't describe how many times I needed to reach my wife, and she wouldn't answer her phone because she didn't hear the ring, so I would ping her phone using Find My, and she would call me back immediately. We've been using this feature now for 10 years. In fact, before I bought her an Apple Watch, the only way for me to get in touch with my wife was to ping her iPhone via Find My iPhone and then wait for her to call me back (she did usually within less than a minute).
There have been times when we had real emergency, and this one feature allowed us to get in touch with each other quickly, whereas without this feature, one or the other person would have been oblivious of an emergency in progress. One time, my 2-year-old son was knocked down unconscious onto a concrete floor by one of his friends when my wife was with him. My phone was not on me and was on silent. She pinged my iPhone, and I called her back to learn what had happened. My wife was in such a distressed state because of my son being unconscious that she couldn't drive or even explain to me where they were. I was able to locate them using Find My iPhone, plot out their location on the Apple Maps, using the Find My iPhone feature, and then I rushed them both to the Children's hospital ER. If it hadn't been for Find My, that incident could have ended much worse than it did.
Stop using
privacy concerns to justify shortcomings in the Apple ecosystem. Again, if you are afraid of being tracked by an AirTag belonging to your family member, don't agree to join Family Sharing. As simple as that.