I do not believe there is an IHIS variable that gives the highest education level by family, but such a variable would be easily constructed by finding the maximum EDUCREC2 value (excluding ‘Unknown’ values) grouped by SERIALand FAMNUMFAMREC. FAMNUMFAMREC is the IHIS variable name for the NHIS FMX variable. IHIS offers an NHIS concordance search tool for finding IHIS equivalents of NHIS variables. Within a variable, you can click on the Source tab and see a list of which NHIS variables were used to create the IHIS variable.
I hope this helps.