When we read that two twins would age differently when one moves with relativistic speeds. i.e. When one twin travels at speed near to speed of light then the twin on earth would see that time for the travelling twin has slowed down. Thats what we say time Dilation. Similar is the case with the other twin. He may also say on returning back that time had slowed for the twin on earth. But his claim is refused because he was initially and finally in a non inertial frame. But what about the time when he was moving with constant velocity. At that time he was moving in an inertial frame. Why does it happen then that what he sees is false and the OP is true??