A video uploaded on Tuesday suggests that the Face ID system on Apple's iPhone X could be fooled not just by twins, but by any family member who bears enough resemblance.
In the the clip, a woman unlocks her phone using Face ID, locks it again, then hands it to her 10-year-old son. The son unlocks it on his first try.
In its current incarnation, Face ID is only able to store one face at a time, meaning that the iPhone made a false match between people of two different ages and sexes.
The technology is meant to adapt to changes in appearance, such as aging, makeup, and facial hair, as well as accessories like hats, scarves, and some sunglasses. That leniency could be what allows two family members to pass for each other, at least when they have a similar facial structure.
Shortly after the iPhone X's launch, it became common to test Face ID with identical twins. Sometimes it passed, other times not.