Recently I have been trying to understand the Special Relativity and Time Dilation. From, my understanding, if a person is moving with a constant velocity "v" with respect to a person not moving then both are moving relative to each other and experience each of their own clocks faster than the other. So, there arises the Twin Paradox problem.
But, from what I have understood, the solution lies in acceleration, whenever the person who is moving with constant velocity, "accelerates" either upon return journey to Earth (Twin paradox problem) or during at any point, acceleration changes the frame of reference of the moving person. Hence, the extra time elapsed to person staying on Earth
So my question is Whether somebody moving without any acceleration,in a constant velocity (closer to light speed) age less than the person staying still OR they will age simultaneously in the same rate, since both of their clocks run faster, looking from each others perspectives,because of Symmetry
PS : I don't have much of a background in Physics, forgive any misunderstanding from my part.