[lozenge]

If you want to teach Face ID to reject masks, you need to make some masks. Similarly, if it needs to be taught to reject a twin, you need dozens of twins. And if it starts labelling people incorrectly as their twins, is it worth it?

Perhaps they can sidestep this by offering a specific twin learning feature.

[hanspeter]

Twins are just examples of two people with very similar faces. If Apple are able to train Face ID to distinguish between 6 billion different faces they will also be able to distinguish faces of twins.