http://www.techradar.com/news/this-10-year-old-unlocked-his-mothers-iphone-x-using-face-id

Apple said its new Face ID unlock system on the iPhone X would only find an issue every one in a million cases, but we've now already heard word of a problem.

A 10-year-old has unlocked his mother's iPhone X using the Face ID feature and it looks like it thinks the child's face is similar enough to his parent's to be able to unlock the phone.