Multiplayer Chunks problem

Help please ! When I go to my world I can see my world perfectly fine but when my friend joins my world they see my world differently. There in a completely different world and the chunks wont load properly. I dont know if its the chunks or something Im not sure. When I join them, there worlds are fine but when they join mine. My house and stuff has a Mansion on top of it and stuff. Please help I cant play the game as fun without my brother or any of my friends. Thanks