I find the concept of becoming brothers in a culture very interesting. I read that Native Americans had practices to become 'blood brothers', and I hear south-western Asian immigrants/descendants often refer to each-other as 'brothers', though it doesn't seem to hold a lot of weight as it gets used seemingly rather lightly.
Is referring to your friend in China as 'brother' a common thing to do and does it actually confer a bond/respect? Is the same done for sisters?