Although SAFR can't differentiate identical twins, it was able to differentiate brothers whom iPhone X’s Face ID failed to differentiate.  SAFR's recognition threshold can be configured to detect very small differences between two faces, this configuration would result in a high percentage of false negatives.  By default this setting provides more tolerance to small differences between the stored identity and presented face.

Settings used to control the difference that SAFR tolerates when matching two faces is set as "Identity Recognition Threshold" in Recognition settings.  Adjusting this value higher (to the right) results in SAFR being more tollerate of the difference between faces.  

The setting Proximity Threshold Allowance will result in SAFR reporting a % match confidence when faces are close but not above the recognition threshold which may be useful to report close but not certain matches such as non-identical twins.