The Vampire King's Runaway Bride

Ruth was working as a hotel maid five years ago and walked into the wrong room on a blood moon night. It was Arthur's, the Vampire King, and the pull between mates did the rest. She was gone before morning. She has been raising the boy alone since. Leo is half vampire and has a rare condition where light hurts him, and the treatment costs more money than a woman in her position will ever put together. A well paid job comes up and it turns out to be at Arthur's castle. He knows what she is the moment he sees her, and he is still angry about the morning she disappeared, so he makes her working life cold and hard. She takes it, because of what Leo's treatment costs. Ruth's aunt, who wants money, sells the boy to the Exorcism Courtyard. Arthur feels his own blood in danger and gets there while Ruth is still on the ground with her body over her son. He breaks their defences open shouting to know who dared touch his child. After that he keeps the two of them, including against a noblewoman at court who resents Ruth's place beside him.