Piccolo and Kami are one and the same. Piccolo is embodiment of all the negative energy that's inside of Kami. They were once one being but split in two. That's why they always share a common bond. If Piccolo dies then Kami dies with the dragonballs, and if Kami dies then Piccolo also dies. But Piccolo and Kami don't get along.

Long before Piccolo was seprated from Kami, he went to the Guardian of Earth to ask for his place. Former guardian wasn't impressed what he saw in Kami - a young warrior from Namek. He didn't want to give his place to anyone who was unworthy. The Guardian said that there is a great evil in his heart and if he wishes to take his place he must get rid of it. Guardian's words touched him because he always felt a darker nature inside of him, and Guardian confirmed this. Only through intense trainning he was able to separate himself from that dark force. The dark force became Piccolo. With his heart pure Kami was able to take Guardian's place, but King Piccolo with his evil ambition escaped to earth. But before he could carry out his evil plans, a mysterious boy appeared, and that boy was Goku. Goku defeated King Piccolo. As his desparate act King Piccolo preserved himself by transforming his essence into a single egg, and like that Piccolo who we now in these series was born. That's why Piccolo looks more younger then Kami, thou they are the same person.

Later on they fuse back into one person to defeat the androids and to find what is Cell... and after this fusion they can never be separated again, which also means the loss of dragonballs and with no guardian of earth at that moment.