I do agree with those above who said you should make 100% sure this guy is truly with the Census Bureau before answering his questions. And as has already been noted, how are they going to know if you lie in your responses? If they already had the information, they wouldn't have to be asking you for it in the first place. Just BS the guy and get him off your back. It's not a battle worth fighting.
Of course, if the census taker got the information wrong...that can lead to speculation. I suspect that's how my dh's family name got changed. Census taker didn't know how to spell and the family was illiterate...LOL