Surname not present in father's passport

[a_d_2]

My father never used surname in his official name. So all his documents like high school certificate, PAN card etc has his name as "first-name Middle-name". So even his passport does not have surname mentioned. Only first name and middle name is mentioned. As none of his documents has surname present so he cannot get passport with Surname.

In all my documents father name has surname i.e. father name is "first-name Middle-name Surname".
So in my passport father name has his surname.

I am on L1 visa. Can i sponsor B2 for my father even if my passport has surname in father's name but my father passport does not have surname?

[immihelp]

It is best to have last name in the passport.

Otherwise, his name will be
First Name = FNU
Last Name = His current "First Name + Middle Name"

This will continue to create issues for him at every step he has to deal with anything related to the U.S.