Answer:
I go up and down at the same time. Up towards to sky and down towards the ground. What am I?
I can never be stolen from you. I am owned by everyone. Some have more some have less.
I am always in front of you but you will never see me
As I went over London Bridge I met my sister Jenny; I broke her neck and drank her blood and left her standing empty.
Goes over all the hills and hollows, Bites hard, but never swallows.
It has no top or bottom, but it can hold flesh, bones, and blood all at the same time.