Emperor Hux is the Resistance's worst nightmare and now he is only one step away from completely annihilating them. In one final desperate attempt to save as much as possible, General Leia asks for negotiations. There she proposes a truce: what's left of the republic may stay independent and in return the Emperor can demand whatever he likes.
Of course Hux isn't interested in a truce, so he requests the one thing he knows to be off limits: General Leia's son Ben. But before Leia is even able to protest, Ben agrees. Now unable to take everything back, Hux finds himself with a new consort by his side.
After the official public claiming ceremony (which is broadcasted all over the First Order territories and of course the Republic, too and starts as dub-con for both, but they get into it) they need to learn how to make this work. In the beginning it's very awkward, but Hux isn't actually a complete asshole, so he never forces himself on Ben and gives him all kinds of gifts. After some time, Ben grows used to his role as a consort (and goes by Kylo Ren from then on) and Hux finds that he has gained a valuable new strategic talent in him.
Also once they decide to have sex it's incredible.
(This can be a/b/o-verse, with Alpha!Hux and Omega!Ben, but it doesn't need to be)