I am referring to yet another version as the classical twin paradox.
In my version the moving apart of the twins is entirely induced by space expansion between them and they move apart each other at a very high speed, conceivably even higher than the local speed of light.
After some time space itself contracts again so that they meet again.
The question is: Is there an age difference between the two?
Is it correct to say that both stayed in the same inertial frame so that there is not even a paradox and no resulting age difference or is the situation more subtle?