Ciel
Your nickname to him : Ciel or Star Boy
Ciel to you:(Y/n) or love
Sebastian:
Your nickname to him: my demon or Buttler
His to you: My love
Alois:
His nickname to you: babe or queen
Your to him: Alois pantsy
Claude:
Your to him: spider or hotz guy (You mostly say this to make his mad lmao)
Him to you: don't have one because come on he's Claude
Finny:
Your to him: my flower Prince
Him to you: (Y/n)-Chan