Force users are kept as slaves and Kylo belongs to Snoke. Snoke is very pleased with the work of General Hux so decides to lend him Kylo for a while as a reward. Hux is very taken with him and enjoys his 'services' fully. When the time comes for Kylo to return to Snoke, Hux isn't sure he wants to let him go...
Snoke/Kylo, Kylux - Slave AU, dub-con