Generic method using instanceof and can it be avoided?

I have the following generic interface/classes

public interface AnInterface <T>{
    T convertToY();
    String getName();
    String getLastName();
}  

public class Foo implements AnInterface<Foo>{
   // some methods specific to Foo  
}   

public class Bar implements AnInterface<Bar>{
   // some methods specific to Bar
} 

I created a generic method as follows (I didn't think it would work but it does)

public static <T> List<Person> getPersons(AnInterface<T> in) {
        System.out.println(map.get(in));
        List<Person> list = new ArrayList<>();
        if (in instanceof Foo) {
            Person p = new Person(in.getName(), in.getLastName());
            p.setId(((Foo) in).getId());
            list.add(p);
        }
        else if(in instanceof Bar) {
            Person p = new Person(in.getName(), in.getLastName());
            p.setCC(((Bar) in).getCC());
            list.add(p);
        }
        return list;
    }  

The issue is that I did not create the classes so I am not sure if doing public class Foo implements AnInterface<Foo> is something usual or not.
So what I am interested in is if there is any issue with the generic method and using instanceof and if there is any problems that can be created. E.g. if I recall correctly we can't use instanceof on collections so I was wondering if I might make it easy to introduce some other bug with this approach.

Note:. I can't modify AnInterface or Foo or Bar