The “paradox” is not really a paradox. Just seems like it at first glance.
The issue with the twins is theoretically there is no way to say which twin is actually moving. Common sense tells us of course the twin in the rocketship is the one jetting off at near light speed while the one on the earth is not moving (in any significant fashion anyway). Relativity tells us this is a wrong assumption. Anyone can say they are at rest and it is the other people who are moving. Those same people could likewise say they are standing still and it is you who is moving. Both are correct and no experiement will solve the problem. If it makes it easier consider a universe with just you and Spaceman Spiff in it. You are approaching Spaceman Spiff at 0.75c. Which of you is moving? Or if both of you are moving who has what speed? No way to tell.
So, our twins seem to be in a paradox because the twin in the spaceship is supposed to take the position that he is standing still and it is the twin on the earth jetting away at near lightspeed. When he gets back to earth he should be older than the earthbound twin but of course that is not the case. The twin in the spaceship is the younger of the two after the trip.
The paradox, IIRC, is explained by acceleration. While at a constant speed the two twins could not say who is moving the reality is the twin on the spaceship experienced an acceleration that the twin on earth did not. This makes it clear who is the moving one and who is the standing still one and we can say who will be the younger when the spaceship returns.