Why do you say husband, boyfriend, girlfriend or wife are relationships that are of more worth than the relationship of a friend?
If it's intimacy. I'll say it's flesh.
If it's secrets I'll say it's choice.
But if you ask me who and what are the contestant coefficient(s) of your equation of life,
that aren't placed there forcefully, like your parents
but are a result of integration through time you spent on this earth...
They are your true friends or maybe just a friend.
But true and constant they are.