I am looking at the Ahnentafel list of my ancestors in the WikiTree API App. What I need to know is why are some of my ancestors listed as '(first name, second name undefined, last name). Can anyone please explain what the word undefined is referring to? Is it about the details of the person's profile name or some other thing. Not all my ancestors on the list have this designation but there are quite a great number who do. Any help appreciated.
Thanks in advance