Please consider the following thought experiment:
Twins are side by side to begin with. They speed off into opposite directions with equal accelerations (and velocities) in magnitude, approach and travel at c/2 for sometime (say 1 year), then slow down with symmetric velocity and acceleration vectors, stop and start coming back in the same manner, till they meet again and stop.
Same (accelerations & velocities) with case 1, but 10 years of (bothways) travel at c/2.
How will relativity handle this and what would each twin think about the other's age ?