My theory is that the Peacock is Clément grandson and one that could've been the heir of the hotel (if not by the MC intruding).
By my math Clément was AT LEAST 81 YEARS OLD (Based when the game takes place + the last check-in on the hotel entrance + the time they [last master] ignored him for 16 years told in the near ending of positive affection route) and ABOUT 100+ YEARS OLD (a child that just got born can't rule a hotel if you know what I mean) by the time the game takes place (somewhere after the Notre Dame cathedral burned down), Asterion does mention mithical creatures being in the staff but never talked about an actually master being one of them.
I think Clément died just after we left the location then that triggered the peacock dreams.