The classic way to control for cultural and in-family influences in studies of human behavior genetics is to look for the rare cases of monozygotic ("identical") twins brought up in separate households after adoption. Those studies of monozygotic twins reared apart (MZA twins) set a MAXIMUM figure for the heritability of any trait of interest--because the genes are as similar as they can be between two different human individuals, but the environments, even in separate households, may not be as maximally different as they could be in influence on the trait in question. There is a whole book about the most famous study of identical twins reared apart, which took place at my alma mater while I was an undergraduate and postgraduate student there (in other subjects).

http://www.hup.harvard.edu/catalog.php?isbn=9780674055469

As some people will remember from the press reports at the time, the most culturally variant upbringing two of the separated twins, Oskar and Jack, studied by the Minnesota researchers received was one twin being raised as a Jew, and the other twin being brought up in Nazi Germany and becoming a member of the Hitler Youth.

http://online.wsj.com/article/SB1000142405270230355210457743...