Culture, Family and Personality

Reflecting on the issue of culture has raised some questions for me about the limits of culture. Where does culture end and particular family traditions begin, and where does personality and personal choice come in?
Families (nuclear and/or extended) and individuals exist in cultures, which makes this a difficult question. Might it help to think of families and individuals as a nexus between cultures--for example if my father is Italian-American and my mother is Latina, my family traditions and practices will span both cultures. I heard an interview a year or so ago with a man who was born in India, grew up in an LA suburb, was educated in British boarding schools, and now lives and works in Japan. Is his culture simply "PoMo," or does the individual transcend culture itself? Does culture inevitably subsume the family and/or individual, or do both exist at once within culture but able to transcend it?
Reasons why families/individuals seem to be able to transcend culture in a limited sense:
Individuals and families can criticize their culture. If culture simply enveloped and determined families and individuals then there would be no means of development beyond interaction with other cultures. But it seems likely that even an isolated group of people constituting a culture (say, living on some island before the invention of radio, satilte, etc) would have various subcultures, and that these subcultures would originally develop because of personal differences. Perhaps this is completely wrong.
Is it possible that a small, isolated group of people could create a mono-culture that made personal or subcultural variation impossible?
Just some thoughts to throw out there for any of my classmates.