Visconti believed that the Duke had deflowered his sister, and some time in 1476 entered a conspiracy against the Duke with Giovanni Andrea Lampugnani and Gerolamo Olgiati, two other Milanese officials.
Visconti was convinced that the Duke had exploited his sister, prompting him to join forces with Giovanni Andrea Lampugnani and Gerolamo Olgiati, two prominent Milanese officials, in a rebellion against the Duke sometime in 1476.