Person A is the heir to the throne of hell/ a vampire coven/ a witch's coven and decides to see what it's like to work like a non royal while he still has the chance and decides to be a personal butler at a house that was looking for servants which is person B's house. 

(people don't know that person A is the heir to the throne because his parents decided to let him have a somewhat normal life until it was necessary to reveal their heir)

Person B's family is a wealthy elite family in hell/the coven. And person B gets person A as his personal butler because his parents wanted him to have one even if he doesn't want one. Person B doesn't like meeting new people unless he is the one to initiate the meeting so at first he doesn't like person A and treats him poorly but over time he gradually starts to get closer to person A and unknowingly starts to fall in love who him. While person B's parents are out of their house on official business Person B sees someone flirting with person A and gets jealous which leads to A being dragged to B's room and they have an argument. While arguing person A also gets angry and accidentally lets it slip that he is the heir to the throne and that he doesn't need to deal with petty arguments over a random person flirting with him. Realizing that he just spilled his secret in a for of rage person A starts to freak out thus losing a small amount of control over his powers and breaks something in the room which further proves to person B that he wasn't lying when he said he was the heir and B helps A calm down and promises not to tell anybody his secret. Their relationship starts to build from there and they become almost inseparable friends (both develops feelings for each other but are to afraid to come out and tell the other). 

Time gap with a random chapter/chapters in between leading to this moment.

There is a big party that will be held at person B's house and because the house is understaffed person A has to be a server at the party. Due to person B's family being elite people in the coven's/hell the party is attacked by rogue demons/witches/vampires who think that  the ruling in hell/the coven's is bad (even though it is good) and that it  should be changed to better empower them(the rogues). Whole the party is being attacked rogues corner person B and attempt to kill him because in their mind killing the only child of the family(and the leaders of the family) will ensure that they can being down the royal's eventually and rule hell/the coven themselves. Person A see's them cornering and trying to kill person B and use's his power to protect person B and his family which also reveals who he is to the family. After the chaos that happened the night before person A and the family has to go to the castle (person A's house) to get shelter and tell person A's father what happened at the party.

Small note: because person A's family wanted him to have a somewhat normal life (as normal as a demon/vampire/witch Prince can get that is) the decided that the public/elite families wouldn't meet their son and only let people know information about his powers. So that is why nobody knew what the Prince looked like. If there were social gatherings that definitely required the presence of the Whole royal family the Prince would be required to wear a mask ( phantom of the opera style) so people wouldn't completly know what he looked like.