You can merge the five Bens by dragging them in the People album on top of each other.
When you rename a person by typing the name below the faces circle, you have to pick the name of the first "Ben" people album rom the list of suggested names. There may be several suggested names, when you start to type a name. And when you do not use one of the suggested names, a new people album will be created. After you name the first photo of Ben, the new album will not directly appear as a suggested name, when you name the next name. It helps to quit Photos and restart to force it to to update the Faces database.
in Photos 5 on Catalina there is an added complication. We are no longer allowed to use the same name on two different faces in the same image. If you have a photo of Ben in front of a mirror, you cannot name the mirror image withe the same name. It will create a second person.