I am taking care of my nephew, he is already 3 yrs. old. He doesn't want to wear diaper, he usually tells me when he wants to poop or pee but sometimes he pees anywhere he want without telling me. I'm having a hard time cleaning because sometimes he run while peeing. When I'm putting diapers on him, later on he'll take it off and leave it somewhere. How can I possibly train him or what can I do about him?