Here is what you get when adding very similar face from “Add face” dialog. In this case “Add to current profile” means add the face to the new profile you have created (not the one that matches the face).
Here is what you get when adding very similar face from “Import…” dialog from “…” menu in upper right of person window. In this case “Add as new” means create new profile with this face.
When adding twins, you have the extra challenge of how to distinguish them when authenticating. As you may have figured out, this is done by using multi-factor authentication. When SAFR gets a face that matches more than one profile, if we are in 2FA mode, we will hold both faces in a list and await the 2nd factor to determine which is the proper match.
If you are not using two factor authentication in general, you can apply 2FA for just persons who you need to have the additional level of differentiation by putting those persons in a special Access Clearance group that requires one of the multi-factor authentication methods. Other person records belonging to an Access Clearance not requiring 2FA will be authenticated as normal.