It is said, often, that we do not choose our family, that we are chosen by it. That familial bonds & obligations trump all others and that betrayal in family systems is among the worst imaginable. That blood is thicker than water, and by inference, the drinks shared between good friends. I call bullshit on the concept entire. The very idea that we, as an organized (kind of) and civilized (for the most part) society that's nearly a decade into the 21st century would allow so much of our fates to be (pre)determined by what are essentially accidents of biology, is ludicrous in the extreme. To place so much more emphasis on nature, leaving nurture coughing in the dust kicked up by the family reunion conga line (no) is irresponsible, unscientific, unhealthy, short-sighted, poorly thought out and dumb. While it is completely possible that every human birth is Dr. Manhattan's "thermodynamic miracle" writ large, there is no logical reason that this qualified revelation of questionable magnitude should dictate future relationships between people. Don't get me wrong; I'm glad he and Laurie came back to Earth, I just don't think I should have to buy a lot more Hallmark cards because of it.
The somewhat dangerous truth, made so because it questions the automatic nature and assumed permanence of our familial relationships (upon which much in our lives is based), is that we choose our families. You don't get to choose your parents, that much is true. At the outset. But you choose to honor them, choose to listen to them, and choose, after your raising up is completed, whether to live because of or in spite of them. You can choose to continue your association with them, or not. So, actually then, you do choose your parents. They certainly chose you. Religions and societal structures, political belief structures, morals and mores are all chosen, and if that's true, every birth is the result of a choice. Births are either dictated by circumstances chosen before sex & pregnancy ensued, or they are planned out to a greater degree by those with the resources and focus to do so. The idea of chalking everything up on the Blackboard of Destiny devalues, in my mind, the importance of the choice. You choose to love someone, and they choose to love you. And behave accordingly. Forced loyalty isn't worth as much as that which is chosen. A choice can be reversed, and as such, it becomes incumbent upon both parties to keep the scales of respect and love balanced out so that no one decides to bail. The potential fragility and impermanence of this arrangement is inherent to its basic worth, dictates such, and requires more attention to maintain. Soap bubbles are cooler than soap.
As a thinking, feeling, evolved human, I make better choices than biology does, anyhow. We are smart enough to have fused our thought processes and our emotional actions/reactions into something only higher animals can accomplish - why subjugate that to accident, sentiment, and chance? Bullshit, says I again. There is no room in life for blood relations who cannot behave as caring, thinking people, and no argument for the feelings of family I have for many who are not related to me in any biological way. I have family in Tennessee, Madison, Atlanta, Chicago, Florida, Indiana, Vegas, and a half dozen other places. I may not talk to you or see you as much as I would like, but hey - that's family for you. And if we don't talk much anymore because it's awkward or because the distance is too big - you're still my family. I decided. (Sorry if I didn't mention your specific geography - it's all about population density.) Now - you could argue that this ersatz family system chose me as I much as I chose it, and that would be true to some extent, but it also contains a level of mutual respect overlooked and undervalued by antiquated familial models.
How much does blood matter? As much as we allow. Aside from genetic prediction of disease, I'm not sure there's much there. Anyone placing a large amount of importance on bloodlines is either in eugenics, horseracing, the Da Vinci Code, or something ending in "dynasty." Or they are clinging to an outmoded concept. You can choose your blood relations, or not. You can marry into a family that means as much, if not more to you, than your birth family. Action is so much more important than this other shit. You can meet people, befriend them, share with them, protect them, have fun together, cry together, and bond over shared experiences, and also choose to call them family. And all of these simply are, as long you treat them as such.
And never stop.