Because when I try to recognize someone I pay attention to the width of the gap in their front teeth.
By moving your face a bit, you can look a lot like another person, and with such features, they all quite similar, however, the teeth are quite easy to spot them out with, since they are tricky to change. Naturally, this gets harder when they get fake teeth put in.
The one on the bottom left has a bigger and more notable nose than the rest. It flares a little.
Also, the hair.
The two on the right have maroon shades, while the top left is bronze, and the bottom left is sort of grey/black.
Also note the partitions. Two have right-hand partitions, one has a center-out and one has a left-hand.
They are fine details to spot, but enough to show they aren't identical. It should be enough to help you differentiate between them, even if you have to stare at them for a bit.
