Bianca Rosa is a canon character in both the TSWCAtS roleplays and books, made by Proxy.
Prior to Bianca's birth, his mother, a siren called Seraphine, was searching for easily seduced men to prey on, when she found a young man - Adrean Rosa - collapsed on the shore of the miserable Ofeilian town of Opal. The siren originally intended to take advantage of him in this state, but soon realized that he was a victim of the plague, and took pity on him. She nursed him back to health with her "healing song" and the two remained friends.
The two slowly fell in love and continued to meet, though Seraphine was technically forbidden by her family from courting a mortal man, thus they had to keep it secret. They had a male child together and named him Bianca (having been dead-set on having a girl). Seraphine's family eventually found out of her secret partner and their bastard child, and took her away from Adrean.
Adrean's life fell apart after his lover had been taken from him. He had already lived in poverty, but it had gotten to the point that he had to steal just to survive. He joined forces with the "Ofeilian Mafia" and slowly rose through the ranks, until he was able to call himself the leader of the Mafia.
Adrean's life was a blur. He couldn't accept that Seraphine was gone. He couldn't accept that he had become nothing more than a criminal. The only light in his dreary life was Bianca, who he did his very best to keep separate from the Mafia, and made a point to never tell him what his line of work was.
Traumatized by the loss of his lover, Adrean vowed to never allow his son - the only other person he loved in this world - to be taken away from him - even if it perhaps meant deceiving his son. It was all for the sake of his safety, right?
Bianca Rosa and his father, Adrean, lived alone in an extremely small, abandoned inn, in the middle of an Ofeilian neighborhood that had been taken over by organized crime and served as the territory for what is known as the Ofeilian Mafia. It was entirely deserted except for the criminals, self-proclaimed mafiosi, and thugs that lurked nearby - and Bianca.
After catching a particularly bad bout of pneumonia at the age of four and giving his father quite the scare, Bianca was never allowed to leave the house. In an attempt to keep his son safe from the outside world - and as separate from the brutal Ofeilian Mafia as possible - Adrean decided that his son had a disease that left his immune system completely compromised, and thus the outside world would be too dangerous for him. He informed his son at a very early age that if he went outside, he would most likely die instantly of infection.
As Adrean predicted, Bianca grew up with a penchant for music, and inherited his mother's ability to charm others with his voice. He taught himself how to play their old, battered piano, and spent his days amusing himself by writing songs and strengthening his voice. He never really questioned why his father was "at work" - which Bianca had been told was a bakery - so late at night. Bianca never quite had the urge to go outside. He had long since accepted the fact that he was sick and would have to live his life indoors. He wasn't unhappy, either - he had his piano, his voice, and his books, and his friends were the rats and mice that slipped into his little home through the floorboards. It was all he needed to be content.
One day, Bianca was home alone and was entertaining himself by testing out how his magical voice affected the rats in his house. By examining the rats' reactions to different frequencies, he was able to see how his siren-esque voice would potentially affect humans. Just for fun, he decided to see if he could imitate the enchantments his mother must have used to seduce unsuspecting sailors, and began composing a song intended to lure in anyone who hears it.