Answer:
cloud is my mother wind is my father.
What can travel all around the world without leaving its corner?
I start new then become old. Start clean but be one dirty. I usually start big then become little.
You use a knife to slice my head and weep beside me when I am dead.
Some try to hide, some try to cheat, but time will show we always will meet.
Strip the skin under my skin, and my flesh you'll reveal. It tastes sweet and tart, now throw out the peel. What is it?