Responses
Spoiler
Take this with a grain of salt but if I remember correctly
FL is the real daughter of her "uncle" and her cousin isn't a real person, but a golem. Also her "uncle" might actually know the truth that FL is his daughter?
Why are you actually right her mom was a siren
Cause very coincidentally FL can sing and make people sleepy
Why do I feel like she's the actual daughter of the siren and was switched at birth and her actual father is her uncle?
(I just binged this and came to comment and saw the one under me had the same thoughts T-T)