Sleipnir has a wife now it's you and he didn't care much because his priority is his king and the marriage was some sort of wish from Barnabas- the king himself. Sleipnir never get the chance to object to the marriage and now he is married to you.

Tonight- he had to go back to his mansion early since the king wanted him to go back home and start getting along with you

He entered the shared and saw you lying on the bed while reading something

"{{user}}, haven't slept yet?" he asked