"Have the affection high enough, remove the slave brand, and then propose. "
You use bramds? Plebian! The most rewarding thing is to have a slave that is working for you of their own free will, even though the way you met is likely:
Bandit: Give Muns!
Player: Nah. *fighting sounds* You're pretty good looking, I'll take you!
Bandit: What do you...? Ropes? ........Oh....crap....
Edit: If it wasn't obvious, this isn't a serious post. Just making it clear to not cause hurt feelings xP