...you can't live with 'em...can you live without them?

I’m feeling discussive today.
More than that, I’m wondering…what makes a family a family?
I mean, there is more to it than just genetics and blood.
I consider my friend, Tracy, to be part of my family and my pets.
Yet, I cannot disregard even those blood ties which I would prefer to forget about.
I believe it is because I am loyal. When it comes down to the nitty-gritty, I am there for my family when they need me.
The unfortunate thing is some of them I can never count on to be there for me. It is only in recent times that I have come to accept this.
I have others in my family to make up for the part that is lacking but, it stings none the less.
Yet, should I act to them as they do to me? No, I am above that. I do not mean to sound smug but, I do not love people and help them only when it is convenient to me…or when I need something from them.
The truth is, I’ve learned long ago not to need anything from them nor do I expect help from them. Indeed, I will always love them but, they do not even know me. They would like to believe that they do but, they have never known me.
My question today is simply this:
What makes family, family and why are blood ties so thin in this day and age?