how to link parental characteristics (restricted variables) to children in NHIS?

I am trying to link some restricted variables at the parental-level to their children in IPUMS-NHIS. For publically available variables, I can do it easily when extracting the data. But for restricted variables, is there a way that I can link parental characteristics to their children? I want to follow a consistent procedure that IPUMS used. Is there a place I can find such procedure or codes?

Thank you.

The Attach Characteristics tool used by the IPUMS extract system uses the MOMLOC, POPLOC, and SPLOC variables to assign characteristics of family interrelationships to records. More information about these variables can be found on this page, via IPUMS USA. Basically, you can use these variables along with the person number variable, PERNUM, to link characteristics of parents within your preferred statistical software.