First of all, it's not exactly clear what is "normal" - this changes from generation to generation and for example the traditional family used to be considered "normal" but now all other kinds of families are normal too.
Second, there is typically a big generational difference between family members, so it's hard to say that they function "as a whole"
For these reasons I don't think this statement is true.
Its a multilateral system of trading in which a country pays for its imports from one country by its exports to another. Hope this answers your question :)
