(:
Ok I found one-R A T E .
Person A is a royal who got turned into a vampire when they were married off to one (who only married them to gain the wealth attached to Person A), but Person A’s personal bodyguard/knight gets killed on a mission (actually set up by the vampire who Person A married, since their bodyguard was deemed a problem). But when their bodyguard died, their dying wish to protect Person A forever took the form of a demon (beings that are lower on the status scale than vampires due to having been created from human sins/tragedy/negative emotions and not ex-humans), Person B, who’s sole reason for existence is to keep Person A safe and happy. Person A starts to develop the same feelings of love for Person B that they had for their bodyguard, but tries to deny their feelings since their vampire spouse always speaks negatively of demons.
so I think-if these vampires are ALSO royalty or at the very least nobility-they probably seek out human nobility to marry/turn, that way they can produce more vampire offspring while maintaining their wealth. The families know because everyone knows of the vampires but just try not to interact with them, but the vampires pay off the families of those who's children have caught their eye VERY handsomely, usually with extremely valuable treasures.