Triplets, three boys. Assume all this happens on the same day and at the same time. Boy A: leaves earth in vessel going .9c in zig-zag directions for thirty days. Returns to earth. Boy B: leaves earth in vessel going .9c but goes in straight line (15 days), turns around and returns to earth after 15 days in that direction. (Returns to earth same moment as Boy A.) Boy C: stays on earth From my understanding of spacetime, Boys A and B should be the exact same age (younger than Boy C) because they moved through spacetime at the same speeds relative to light speed. Direction shouldn't, if my understanding of moving through spacetime is correct, matter in determining the ages of the boys. It should simply concern the speeds at which they moved through spacetime. What am I missing?