[johanj]

Really? It’s been discussed a lot on various podcasts, on Twitter and I’ve heard multiple people IRL talk about that use case and the slightly annoyance it is with the iPhone X.

It is pretty common for spouses to have a finger added on their spouse’s phone for unlocking it with Touch ID, e.g., when you’re driving and get a message, you can give it to your spouse who can reply.

Many parents also have a finger added on their young children’s phones.

None if these scenarios are really possible with Face ID, because you’ll end up training Face ID with two faces. And while phones are usually used by only a single person, it is not an uncommon scenario to have a secondary user.

[mikeash]

Yes, really. I don't listen to technical podcasts, and I haven't seen any Twitter or IRL stuff about it.

Anyway, if you want to have a shared phone like this, get one that has Touch ID. Apple offers both.

Or trust that Apple does this intelligently and doesn't train the facial recognition in this case when the face is too far out of bounds. As other commenters mentioned, I'm pretty sure that's how it works. It's not training based on your wife's face unless she looks a lot like you. And in that case, you want her to be able to unlock your phone, so isn't it a good thing?

[valuearb]

That second face has to look a lot like yours to get adddd via training.

And if you are one of those couples that look alike enough to be able to train the phone, why do you care? You already gave your spouse full access via your passcode.

[mrep]

My girlfriend and I have our fingerprints on each other's phones and it is super useful.

She can change the music on my phone while driving, look up stuff for me to enter into maps, and do everything else with it.