Piccolo is the reincarnation of his father Piccolo Daimaou. Many people think it's a plot hole that Ka,i is still alove after Daimaou is killed. Piccolo retains all of his father's memories and abilities, however, he does have something that his father didn't. A conscience. When Piccolo first appears during the 23rd Tenkaichi Budoukai, he's incredibly brutal and seriously has it in  for Goku. The next time he shows up to assist Goku in defeating Raditz, he still has no feelings for Goku ans would kill him just as soon as he'd kill Raditz.....wich.....uh...he does. But that's besides the point. As he's forced to train Goku's child Gohan to be a warrior, Piccolo becomes attached to Gohan, but neve once shows it.Piccolo finally becomes reformed when he sacrifices his life to save Gohan's. From that moment on, he losses his desire to conquer the Earth. (Sometimes he lets his anger get to the best of him, and says bad things, but he's not serious). Later on, Piccolo merges with Nail increasing his power to 1,000,000 allowing him to go one on one with stage 2 Freiza. And in the middle of the Android saga, he merges with his other half, Kami, and becomes the true original Piccolo once again. His various mergings do not change him

physically, but internally he retains the memories of of both Nail and Kami. After merging with Kami, Piccolo becomes even more philosophical than he normally is, (hard to imagine), and takes actions that put him in danger for sake of the earth, (such as sealing himself Gotenks and Buu in the room of spirit and time). After fusing with Kami, Piccolo makes Kami's Palace his home, and he always has a special place for Gohan in his heart thriugh the rest of the series.