Answer:
Everyone has me and no one can lose me. What am I?
What belongs to you but others use it more than you do?
What gets sharper the more you use it?
I'm the source of all emotion but I'm caged in a white prison.
I am a rock group with four members all of whom died in plane crashes. Who am I?
It has no top or bottom, but it can hold flesh, bones, and blood all at the same time.