How to add FaceID for family members to iPhones We only have cellular phones in our home and with our older phones my wife and I could add TouchIDs to each of our phones, and add our children's fingerprints as well.  So, anyone could quickly use either phone.  It's not just a matter of convenience, but also if there is an urgent matter... perhaps not a 911 emergency, but an emergency none the less, our children can quickly use the phones to get help.

Anyhow, with our new iPhone X, I cannot find how to train it to open for more than one face.  How can we add FaceID for family members to our iPhones now?
The iPhone X currently does not support multi-face authentication. You can only add one face now. It may be or may not be added in the future updates. As per a mail sent by Apple VP Craig Federighi, it's unlikely that Apple will add this in future. You can read the mail from him in below link at MacRumors.

Mail from Craig Federighi