Who is Michelotto, the gooseboy from Mirror Mirror and what is their importance?

Michelotto is the gooseboy at Montefiore. He is responsible for the geese and their care. Michelotto is described as mentally slow with a sweet disposition. His parents, Lucrezia and Cesare Borgia, and, are also his aunt and uncle. Lucrezia refers to her son as "the Punishment" (218).