Creating fixed structures that span across groups of people is incredibly hard. Just take a look at how much work/debate has gone into the taxonomy of life.

Apart from that relationships are context dependent. I can have a father but if he passes away I still have one in some sense but not in another.

I can also have ideas... or friends which can be mutual or not. Heck... even "I" isn't fixed. If I'm sleepwalking it's me but not really me.

My point was: do you know of any OOP language which can fluently handle this without having the object metaphor break down?