Hi
I am not sure I understand your problem correctly. However, I think your problem can be solved using the following solution :
1. You change title of the First Name and Last Name field to Parent First Name and Parent Last Name (it can be changed easily using the Translation function from back-end of the extension) .
2. You can create two extra custom fields and named them as First Name and Last Name.
Hope my explanation is clear to you . If you have other questions, please don't hesitate to ask me .
Thanks,
Tuan