Who said that they registered the birth with baby in hand. Could granny and gramps have done so. I’m not even convinced he was registered properly. It could have been done after the fact.
What happens in the case of births at home, the baby still has to be registered. The certificate at "check the facts" doesn't give the mode or local address of birth.
WOULD HAWAII HAVE A COPY (MICROFILMED OR OTHERWISE) OF THE REGISTRATION REQUEST FORM ITSELF?
If she was 17, remembering when I was 17, her parents probably did register him.