Usually, you become friends with people when you have more in common and more things to relate over. I suppose all strangers are potentially friends but it can be rare to find people you really click with. Then, it hurts like hell if and when you lose them.
I must know someone completely.
Sometimes I wonder if any of us are that interested in another person to know them anywhere near completely. Maybe that's a really cynical point of view. I suppose that's what appeals about a relationship. That you give enough of a shit about each other to really know one another. I don't know that people really do though.
My parents relationship sounded pretty solid to me. My Mum died when I was young. But, when I've asked my Dad really basic things about her, he doesn't always know! They didn't seem to discuss past relationships for instance. Seems kind of weird to me. I guess some relationships are built on shared experiences in the present though.
It's pretty foreign to me. I wish we could rely on people though. It hurts to get close to someone and then lose them.