Family, of course, is not something we choose. Family is not premised on activity — on anything we do — but on the necessity and abstraction of "family." It is something we are born to, damned to, tethered to. Needless to say, we can choose to ignore it: we don't have to interact with our families (my father left when I was 2 and I never saw him again — and yet, by definition, he remains my father; which is to say, his actions don't undo the concept). Family is, by definition, that which happens automatically, before and beyond any and all activity. Our relationship to individual members of our family is mediated by this abstraction: "You're my brother, sister, mother no matter what you do."
Friends are another sort of relationship all together. We choose our friends and they, in turn, choose us. There is no necessity. The relationship exists through activity by both parties (unlike family: a brother is a brother regardless of what he does). Friendship is active. It demands work — a negotiation of, and between, at least two people. (Family, too, involves work — my god, it demands more work than any friendship — but not by definition.)
Friendship, then, is not inherently conceptual or abstract. It is built from worldly interaction, by and within the behavior of all parties.
And yet both family and friends demand an unconditional love. But the conditions of this lack of conditions are different for family than they are for friends.
When I was married, my wife used to get frustrated with me for not calling back my friends — I often go weeks without returning calls. But, to me, that is the definition of a friend: a person you don't have to call back. Family implies a certain duty. Work, of course, holds a paycheck over my head — so I call back. But friends? Ah, friends are people I choose — and so I can choose not to call them back.
Indeed, far from being a rebuke of that friend, my decision not to call back is an affirmation of my friendship. If I feel obliged, then the friend is no longer a friend, no longer someone I choose to be with but someone I must be with — that friend becomes family. And I don't want my friends to become family. I already have those obligations, those duties, those very special forms of torture and pleasure.
No, what I want from a friend is all the complication and messiness of choice, of negotiation, of desire and will. I want to want to be with this or that person; I want that person to fuel me, vitalize me, just as I want in turn to fuel and vitalize him or her.
When I am being a real dud — when I'm slow witted, cranky, depressed — I feel it is my obligation to avoid my friends. My mother, however, is different: she can get my worst self. But not my friends. My friends deserve, need, my best self. And they feel the same way.
Of course, things are not always so clear cut. Sometimes, friends do become family and that can be beautiful — to have a choice become a necessity. This often happens with old friends — there's no longer that immediacy of vitality but there is something else there, an abiding love.
Other times, a friend may be feeling shitty but I can try to make him feel better so that I can get him back to his vital, witty, zestful self. Which is to say, the condition of love for my friends is different than the condition of love for my family. With family, I'm just "there for them." With friends, I'm there for them, too — but so they can get back to the on-going negotiation, that mutual fueling and enlivening.