The subject of relativity has been haunting me for while now. Everytime i feel i understand a concept, there comes questions withtin that contradict the undestanding. Have been trying to digest the time dialation & symmetry of how it is felt mutually by observers in two different frame of reference. Let me try and present a simple thought experiment below. Let there be 2 frames of references Fa & Fb. Each of these reference frames be infinite in length. Now let us line up kids who are 5 years old in both the reference frames with clocks in their hand. Assume we have them lined up infinitely on each reference frame facing each other, with all their clocks synchronized. Let Frame Fa & Fb be moving in oppposite directions each with velocity v/2 (for an external observer), which makes each reference frame feel that other one is travelling with velocity v towards the opposite direction. At the origin of the corindates we have KidA (on frame A) and KidB (on Frame B). While they pass each other, we set Ta=Tb=0 (clocks are synchronized). Question is: Looks like everything is symmetric here. After time passes by, will KidA see all opposite frame kids to be growing younger than him? What about KidB then? Will he see the same symmetry when he looks at kids on the other frame. How can both be correct here when kids within the same frame of reference be all of the same age. May be the very way i am thinking of the problem itself is wrong. Would like to see some explanation to understand the correct experience in such a scenario.