we run into the same problem. I got RFE yesterday. family household registry is 戶口本. I don't think they care about your parents birth cert. They want to make sure you are qulified to file I-130 for them.
Are your field office in SF? It looks like there is a policy shift. It is rarely a problem a few years ago and it totally caught me off the guard.
Send me pm if you want to discuss it
good luck!