The word or idea of "family" is so universal and accepted it would almost seem that any discussion on it would have to be personal. I believe the idea of family, however, is quite a bit more complicated (or at least should be) than what it may seem.
Family is essentially just the blood connection between people, so it is basically the sharing of genetic material. Why is it then that we have such a large emotional connection to family? (Or at least the majority of people have or are expected to.)
I think our natural devotion to family is obvious; it stems from our survival instincts and is one of the reasons we are the most successful species on the planet. Our strong social bonding and tendency to help each other have catapulted us way ahead of any previous or current living creature. So over time it would not surprise me that natural selection has only strengthened that family bond.
Having realised the value of family to our species, and the emotional bonding as a result (emotions will ensure we are socially constructive as opposed to focused just on our own individual existence), I think the personal value placed on the genetic definition of family is questionable.
A lot of value is placed upon blood connections between people: we value that person if for nothing else then purely for that connection. I would argue that there is a value to that connection, but it isn't anything comparable to the social expectant value it holds. I think the perfect example is that of adoption. The child becomes a part of a "family", even though there is no genetic connection at all (except for some artificial selection). That child will grow up with the same value placed upon family members as those who are genetically connected to their up-bringers.
This example alone indicates something transcendent of the traditional idea of family links, perhaps with a connection to the earlier source of family in reference to survival instinct. As we know, that survival connection should break down or at least reduce when we become independent, but it doesn't reduce enough or even at all. So where is the value that natural families share with orphan families coming from?
This, I think, is the direct relationships we build with people. And beyond that is the inevitable conclusion that the people you have grown up with will have imprinted part of themselves onto you. We have a pure connection to these people because they are inevitably a part of what makes us up. I think this is evident in abusive households where a connection is reversed into adversary and so the "family" members' contribution to that person's makeup is stopped or restricted. The relationship is no longer something that is invaluable; it becomes disposable because it no longer contributes positively to lives. This is also demonstrable in the instance of family connections being broken due to massive changes to personal beliefs and principles - that deeper understanding of each other is compromised and middle ground is destroyed.
Essentially I think the value of the idea of traditional family is limited. I think what transcends the genetic link and is far more valuable is the personal connection between family members and the inevitable valuable exchange that goes on. This is where I think people who are referred to as "friends" could also fall into what I think is a more real description of family - reducing the importance of genetic link and emphasizing the importance of personal relationships.