my daughter can unlock my iphone x using face id??

I suggest that you make a Genius Bar appointment at the nearest Apple store and bring your phone, and your daughter, and demonstrate what you have found to Apple. I figure they would be interested if you can duplicate that behavior.

Are you sure she is unlocking it, or is it that the device is not locking right away, and her picking it up is just waking the device up. If you go to Settings>Display & Brightness>Auto-Lock, what is the setting there? How long after you finish with the device is your daughter accessing it? Are you manually locking the device when you get done with it?

Then please take the time to make an appointment at the Genius Bar to have this examined. It would seem very strange that a daughter could unlock a mother's phone. It would seem to be an anomaly, and I'll bet Apple would be interested in that information.

just for my information....does she know your passcode to get into the phone. If not ignore what i typed below

its like the one video of the faternal twins unlocking the phone.......

you set up your face.....

your daughter pick up your phone

scan equals no match...stays locked....

she inputs the passcode it adds the changes it saw with last scan

you guys keep repeating this and you get a scan that uses both your faces

unlocks for both of you

you do this enough the neural engine learns both faces are the owner

If you don’t want her to be able to unlock it might want to change passcode and redo face scan would hope that might fix it. If your not worried it allows your kid to access your phone in an quick emergency.

Hi

Change the auto lock time in settings.

Is she just using your passcode?

Go to i books download iPhone X guide it.s Free.

Cheers

Brian 🇬-1F1E7;

My thoughts as well Chris.