Traditional Culture Encyclopedia - Hotel reservation - What is the relationship between Caesar and Lucrezia?

What is the relationship between Caesar and Lucrezia?

It's brother and sister.

Caesar is her brother and Lucrezia is her sister. They are called Borgia and his sister.

Two people are followers of a group. Worked as a waiter in a hotel in Akihabara. Their real identity is a well-known intelligence dealer in the underground society.