Hux becomes Emperor and takes Kylo as his consort. He has been reading up on Imperial tradition throughout the ages and comes across a ritual where the Emperor impregnates his consort in front of his entire court as a way to ensure a strong heir is conceived. Kylo can be into it or not but has no real choice either way.

Bonus points if Hux keeps on his elaborate Emperor robes during the ritual but Kylo has to be completely naked.