Since this form is mostly a declaration of family members that you could possibly sponsor in the future, you could say in the letter that you have no intention of ever sponsoring your father. BUT if you put this and then someday reunite with your father and want to sponsor him, you most likely will not be able to.
who gave you that information. The information could be merely a database to distinguish individuals with same names born on same day and same city. In such situation only way to separate them is by parent's names