How to change module Mandatory field

How to change module Mandatory field

We have a custom module called Parents/Guardians. When it was set up the field called "Parent/Guardian Name" was made mandatory. However, when I create a Form, this field cannot be taken out of the form. I want separate fields for "First Name" and "Last Name" so that we can export into our email platform. Where can I change this to make the Last Name field mandatory instead?