bff? among guys?

So I am setting at best friend house and just wonder on how did I really become his best friend. It all doesn't make any sense of why we cross each others path. i really don't know how. It all doesn't make sense. we're so different from each other. Best Friend Forever type deal? or what.. just friends till i move and our lives change? or when we get married our two familys will hang out with eeach other. i really hope the latter. He's ddefinitely my best friend. and I hope im his.