Yes, family members can give all kinds of dubious reasons why they don't have a birth certificate. In my family, the story was that the records office where my grandmother was born had burned down. Real reason, however, was she was very likely an immigrant from Canada and didn't want people to know. So if HK has a birth certificate for him then sounds like he was born in HK- and pretty sure in 1960 everyone was recording birth certificates, China and HK. 1960 means dad is only 57-58, not all that long ago.